Physics

Question: Law of motion Newton

Newton's First Law of Motion:

I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

This we recognize as essentially Galileo's concept of inertia, and this is often termed simply the "Law of Inertia".

Newton's Second Law of Motion:

II. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.

This is the most powerful of Newton's three Laws, because it allows quantitative calculations of dynamics: how do velocities change when forces are applied. Notice the fundamental difference between Newton's 2nd Law and the dynamics of Aristotle: according to Newton, a force causes only a change in velocity (an acceleration); it does not maintain the velocity as Aristotle held.

This is sometimes summarized by saying that under Newton, F = ma, but under Aristotle F = mv, where v is the velocity. Thus, according to Aristotle there is only a velocity if there is a force, but according to Newton an object with a certain velocity maintains that velocity unless a force acts on it to cause an acceleration (that is, a change in the velocity). As we have noted earlier in conjunction with the discussion of Galileo, Aristotle's view seems to be more in accord with common sense, but that is because of a failure to appreciate the role played by frictional forces. Once account is taken of all forces acting in a given situation it is the dynamics of Galileo and Newton, not of Aristotle, that are found to be in accord with the observations.

Newton's Third Law of Motion:

III. For every action there is an equal and opposite reaction.

This law is exemplified by what happens if we step off a boat onto the bank of a lake: as we move in the direction of the shore, the boat tends to move in the opposite direction (leaving us facedown in the water, if we aren't careful!).

Question: Trajectory motion

Freefall

In the absence of frictional drag, an object near the surface of the earth will fall with the constant acceleration of gravity g. Position and speed at any time can be calculated from the motion equations.

Illustrated here is the situation where an object is released from rest. It's position and speed can be predicted for any time after that. Since all the quantities are directed downward, that direction is chosen as the positive direction in this case.

Vertical Trajectory

Vertical motion under the influence of gravity can be described by the basic motion equations. Given the constant acceleration of gravity g, the position and speed at any time can be calculated from the motion equations:

Horizontal Launch

All the parameters of a horizontal launch can be calculated with the motion equations, assuming a downward acceleration of gravity of 9.8 m/s2.

General Ballistic Trajectory

The motion of an object under the influence of gravity is determined completely by the acceleration of gravity, its launch speed, and launch angle provided air friction is negligible. The horizontal and vertical motions may be separated and described by the general motion equations for constant acceleration. The initial vector components of the velocity are used in the equations. The diagram shows trajectories with the same launch speed but different launch angles. Note that the 60 and 30 degree trajectories have the same range, as do any pair of launches at complementary angles. The launch at 45 degrees gives the maximum range.

IndexTrajectory conceptsCalculation

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Will it clear the fence?

The basic motion equations can be solved simultaneously to express y in terms of x.

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Where will it land?

The basic motion equations give the position components x and y in terms of the time. Solving for the horizontal distance in terms of the height y is useful for calculating ranges in situations where the launch point is not at the same level as the landing point.

Where will it land?

The basic motion equations give the position components x and y in terms of the time. Solving for the horizontal distance in terms of the height y is useful for calculating ranges in situations where the launch point is not at the same level as the landing point.

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Launch Velocity

The launch velocity of a projectile can be calculated from the range if the angle of launch is known. It can also be calculated if the maximum height and range are known, because the angle can be determined.

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Launch Velocity

The launch velocity of a projectile can be calculated from the range if the angle of launch is known. It can also be calculated if the maximum height and range are known, because the angle can be determined.

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Angle of Launch

Variation of the launch angle of a projectile will change the range. If the launch velocity is known, the required angle of launch for a desired range can be calculated from the motion equations.

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Question: Momentum

Momentum

The sports announcer says, "Going into the all-star break, the Chicago White Sox have the momentum." The headlines declare "Chicago Bulls Gaining Momentum." The coach pumps up his team at half-time, saying "You have the momentum; the critical need is that you use that momentum and bury them in this third quarter."

Momentum is a commonly used term in sports. A team that has the momentum is on the move and is going to take some effort to stop. A team that has a lot of momentum is really on the move and is going to be hard to stop. Momentum is a physics term; it refers to the quantity of motion that an object has. A sports team that is on the move has the momentum. If an object is in motion (on the move) then it has momentum.

Momentum can be defined as "mass in motion." All objects have mass; so if an object is moving, then it has momentum - it has its mass in motion. The amount of momentum that an object has is dependent upon two variables: how much stuff is moving and how fast the stuff is moving. Momentum depends upon the variables mass and velocity. In terms of an equation, the momentum of an object is equal to the mass of the object times the velocity of the object.

Momentum = mass velocity

In physics, the symbol for the quantity momentum is the lower case "p". Thus, the above equation can be rewritten as

p = m v

where m is the mass and v is the velocity. The equation illustrates that momentum is directly proportional to an object's mass and directly proportional to the object's velocity.

The units for momentum would be mass units times velocity units. The standard metric unit of momentum is the kgm/s. While the kgm/s is the standard metric unit of momentum, there are a variety of other units that are acceptable (though not conventional) units of momentum. Examples include kgmi/hr, kgkm/hr, and gcm/s. In each of these examples, a mass unit is multiplied by a velocity unit to provide a momentum unit. This is consistent with the equation for momentum.

Momentum is a vector quantity. As discussed in an earlier unit, a vector quantity is a quantity that is fully described by both magnitude and direction. To fully describe the momentum of a 5-kg bowling ball moving westward at 2 m/s, you must include information about both the magnitude and the direction of the bowling ball. It is not enough to say that the ball has 10 kgm/s of momentum; the momentum of the ball is not fully described until information about its direction is given. The direction of the momentum vector is the same as the direction of the velocity of the ball. In a previous unit, it was said that the direction of the velocity vector is the same as the direction that an object is moving. If the bowling ball is moving westward, then its momentum can be fully described by saying that it is 10 kgm/s, westward. As a vector quantity, the momentum of an object is fully described by both magnitude and direction.

From the definition of momentum, it becomes obvious that an object has a large momentum if either its mass or its velocity is large. Both variables are of equal importance in determining the momentum of an object. Consider a Mack truck and a roller skate moving down the street at the same speed. The considerably greater mass of the Mack truck gives it a considerably greater momentum. Yet if the Mack truck were at rest, then the momentum of the least massive roller skate would be the greatest. The momentum of any object that is at rest is 0. Objects at rest do not have momentum - they do not have any "mass in motion." Both variables - mass and velocity - are important in comparing the momentum of two objects.

The momentum equation can help us to think about how a change in one of the two variables might affect the momentum of an object. Consider a 0.5-kg physics cart loaded with one 0.5-kg brick and moving with a speed of 2.0 m/s. The total mass of loaded cart is 1.0 kg and its momentum is 2.0 kgm/s. If the cart was instead loaded with three 0.5-kg bricks, then the total mass of the loaded cart would be 2.0 kg and its momentum would be 4.0 kgm/s. A doubling of the mass results in a doubling of the momentum.

Similarly, if the 2.0-kg cart had a velocity of 8.0 m/s (instead of 2.0 m/s), then the cart would have a momentum of 16.0 kgm/s (instead of 4.0 kgm/s). A quadrupling in velocity results in a quadrupling of the momentum. These two examples illustrate how the equation p = mv serves as a "guide to thinking" and not merely a "plug-and-chug recipe for algebraic problem-solving."

Question: Kirchoffs current law and Kirchoffs voltage law

Question; Ohms law

Question: Energy released by in heating

Q = m x C x T. Where.... Q = Quantity of Heat (Released or Absorbed). Joules, calories or Btu. m = Mass (grams) of substance being heated, cooled or changing state. C = Specific Heat Capacity (J/g/C; cal/g/C; Btu/lb/F). (Also, Molar C = Molar Heat Capacity J/mol.K (or C). T = Difference in Temperature.(TC; or TF).

When ice falls from the height it kinetic energy in converterted in melting up if part of weight of Ice

1/2mV2 =- mCt

Question: Heating and cooling

Question: Molar eqaution and avagadros constant

Do chapter 7 practice test pdf/My documents

Question: Nuclear fission and nuclear fusion

Nuclear fusion and nuclear fission are two different types of energy-releasing reactions in which energy is released from high-powered atomic bonds between the particles within the nucleus. The main difference between these two processes is that fission is the splitting of an atom into two or more smaller ones while fusion is the fusing of two or more smaller atoms into a larger one.

Comparison chart Embed this chart

Nuclear FissionNuclear Fusion

Definition

Fission is the splitting of a large atom into two or more smaller ones.

Fusion is the fusing of two or more lighter atoms into a larger one.

Natural occurrence of the process

Fission reaction does not normally occur in nature.

Fusion occurs in stars, such as the sun.

Byproducts of the reaction

Fission produces many highly radioactive particles.

Few radioactive particles are produced by fusion reaction, but if a fission "trigger" is used, radioactive particles will result from that.

Conditions

Critical mass of the substance and high-speed neutrons are required.

High density, high temperature environment is required.

Energy Requirement

Takes little energy to split two atoms in a fission reaction.

Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion.

Energy Released

The energy released by fission is a million times greater than that released in chemical reactions, but lower than the energy released by nuclear fusion.

The energy released by fusion is three to four times greater than the energy released by fission.

Nuclear weapon

One class of nuclear weapon is a fission bomb, also known as an atomic bomb or atom bomb.

One class of nuclear weapon is the hydrogen bomb, which uses a fission reaction to "trigger" a fusion reaction

Fission and FusionTable of Contents

1. 1. Introduction

2. 2. Fission

1. 2.1. Critical Mass

3. 3. Fusion

4. 4. Outside links

5. 5. References

6. 6. Contributers

The energy harnessed in nuclei is released in nuclear reactions. Fission is the splitting of a heavy nucleus into lighter nuclei and fusion is the combining of nuclei to form a bigger and heavier nucleus. The consequence of fission or fusion is the absorption or release of energy.

1. 1. Introduction

2. 2. Fission

1. 2.1. Critical Mass

3. 3. Fusion

4. 4. Outside links

5. 5. References

6. 6. Contributers

Introduction

Protons and neutrons make up a nucleus, which is the foundation of nuclear science. Fission and fusion involves the dispersal and combination of elemental nucleus and isotopes, and part of nuclear science is to understand the process behind this phenomenon. Adding up the individual masses of each of these subatomic particles of any given element will always give you a greater mass than the mass of the nucleus as a whole. The missing idea in this observation is the concept called nuclear binding energy. Nuclear binding energy is the energy required to keep the protons and neutrons of a nucleus intact, and the energy that is released during a nuclear fission or fusion is nuclear power. There are some things to consider however. The mass of an element's nucleus as a whole is less than the total mass of its individual protons and neutrons. The difference in mass can be attributed to the nuclear binding energy. Basically, nuclear binding energy is considered as mass, and that mass becomes "missing". This missing mass is called mass defect, which is the nuclear energy, also known as the mass released from the reaction as neutrons, photons, or any other trajectories. In short, mass defect and nuclear binding energy are interchangeable terms.

To calculate the energy released during mass destruction in both nuclear fission and fusion, we use Einsteins equation that equates energy and mass:

E=mc2

with m=mass (kilograms), c=speed of light (meters/sec) and E=energy (Joules).

Example

Find the energy available in 0.2500 kg of hydrogen gas.

E=mc2

E=(0.2500 kg)(299792458 m / s)2

E=2.247X1016 Joules

Note it is impossible to acquire 100% of the potential energy available in the nucleus of the hydrogen atom unless the same amount of antimatter(positron) is reacted with the hydrogen. The result is the complete annihilation of the hydrogen and the release of 2.247X1016 Joules of energy. In the nuclear reations, m becomes m, which is the difference of the end and start mass of the nucleus. The difference in mass is the mass lost and energy released during a nuclear reaction. Note that the energy released from a nuclear fusion or fission is not the same as an entire molecule being annihilated so the energy released is much smaller, but is still significantly larger than the energy released from the average chemical oxidation reaction.

Binding energy per nucleon of common isotopes.

Fission

Fission is the splitting of a nucleus that releases free neutrons and lighter nuclei. The fission of heavy elements is highly exothermic which releases about 200 million eV compared to burning coal which only gives a few eV. The amount of energy released during nuclear fission is millions of times more efficient per mass than that of coal considering only 0.1 percent of the original nuclei is converted to energy. Daughter nucleus, energy, and particles such as neutrons are released as a result of the reaction. The particles released can then react with other radioactive materials which in turn will release daughter nucleus and more particles as a result, and so on. The unique feature of nuclear fission reactions is that they can be harnessed and used in chain reactions. This chain reaction is the basis of nuclear weapons. One of the well known elements used in nuclear fission is Uranium-235. When Uranium-235 is bombarded with a neutron, the atom turns into Uranium-236 which is even more unstable, resulting in the nucleus splitting into daughter nuclei such as Krypton-92 and Barium-141 and free neutrons. The resulting fission products are highly radioactive, commonly undergoing beta-minus decay.

Nuclear fission is the splitting of the nucleus of an atom into nuclei of lighter atoms, accompanied by the release of energy, brought on by a neutron bombardment. The original concept of this nuclei splitting was discovered by Enrico Femi in 1934who believed transuranium elements might be produced by bombarding uranium with neutrons, because the loss of Beta particles would increase the atomic number. However, the products that formed did not correlate with the properties of elements with higher atomic numbers than uranium (Ra, Ac, Th, and Pa). Instead, they were radioisotopes of much lighter elements such as Sr and Ba. The amount of mass lost in the fission process is equivalent to an energy of 3.20 x 10-11 J.

Example

Consider the neutron bonbardment

23592U+01n23692Ufissionproducts

which releases 3.20 x 10-11 J per 235U atom.

How much energy would be released if 1.00g of 235U were to undergo fission.

1.00g 235U x 1 mole 235U x 6.022 x 1023 atoms 235U x 3.20 x 10-11 J = 8.20 x 1010 J

235 g 235U 1 mole 235U 1 atom 235U

So, as you can see, fission of a small amount of atoms can produce an enormous amount of energy, in the form of warmth and radiation (gamma waves). When an atom splits, each of the two new particles contains roughly half the neutrons and protons of the original nucleus, and in some cases a 2:3 ratio.

Critical Mass

The explosion of a bomb only occurs if the chain reaction exceeds its critical mass. The critical mass is the point at which a chain reaction becomes self-sustaining. If the neutrons are lost at a faster rate than they are formed by fission, the reaction will not be self-sustaining. The spontaneous nuclear fission rate is the probability per second that a given atom will fission spontaneously--that is, without any external intervention. In nuclear power plants, nuclear fission is controlled by a medium such as water in the nuclear reactor. The water acts as a heat transfer medium to cool down the reactor and to slow down neutron particles. This way, the neutron emission and usage is a controlled. If nuclear reaction is not controlled because of lack of cooling water for example, then a meltdown will occur.

Fusion

Nuclear fusion is the joining of two nuclei to form a heavier nuclei. The reaction is followed either by a release or absorption of energy. Fusion of nuclei with lower mass than iron releases energy while fusion of nuclei heavier than iron generally absorbs energy. This phenomenon is known as iron peak. The opposite occurs with nuclear fission.

The power of the energy in a fusion reaction is what drives the energy that is released from the sun and a lot of stars in the universe. Nuclear fusion is also applied in nuclear weapons, specifically, a hydrogen bomb. Nuclear fusion is the energy supplying process thatoccurs at extremely high temperatures like in stars such asthe sun, where smaller nuclei are joined to make a larger nucleus, a process that gives off great amounts of heat and radiation. When uncontrolled, this process can provide almost unlimited sources of energy and an uncontrolled chain provides the basis for a hydrogen bond, since most commonly hydrogen is fused. Also, the combinationof deuterium atoms to form helium atoms fuel this thermonuclear process. For example: 2H + 3H 4He + 1n + energy.

However, a controlled fusion reaction has yet to be fully demonstrated due to many problems that present themselves including the difficulty of forcing deuterium and tritium nuclei within a close proximity, achieving high enough thermal energies, and completely ionizing gases into plasma.A necessary part in nuclear fusion is plasma, which isa mixture of atomic nuclei and electrons that are required to initiate a self-sustaining reaction which requires a temperature of more than 40,000,000 K. Why does it take so much heat to achieve nuclear fusion even for light elements such as hydrogen? The reason is because the nucleus contain protons, and in order to overcome electrostatic repulsion by the protons of both the hydrogen atoms, both of the hydrogen nucleus needs to accelerate at a super high speed and get close enough in order for the nuclear force to start fusion. The result of nuclear fusion releases more energy than it takes to start the fusion so G of the system is negative which means that the reaction is exothermic. And because it is exothermic, the fusion of light elements is self-sustaining given that there is enough energy to start fusion in the first place.

Note that scientists have yet to find a method for controlling fusion reactions. Fission reactions on the other hand is the type used in nuclear power plants and can be controlled. Atomic bombs and hydrogen bombs are examples of uncontrolled nuclear reactions.

What Is A Nuclear Reactor?

All nuclear reactors are devices designed to maintain a chain reaction producing a steady flow of neutrons generated by the fission of heavy nuclei. They are, however, differentiated either by their purpose or by their design features. In terms of purpose, they are either research reactors or power reactors.

Research reactors are operated at universities and research centres in many countries, including some where no nuclear power reactors are operated. These reactors generate neutrons for multiple purposes, including producing radiopharmaceuticals for medical diagnosis and therapy, testing materials and conducting basic research.

Power reactors are usually found in nuclear power plants. Dedicated to generating heat mainly for electricity production, they are operated in more than 30 countries (see Nuclear Power Reactors). Their lesser uses are drinking water or district water production. In the form of smaller units, they also power ships.

Differentiating nuclear reactors according to their design features is especially pertinent when referring to nuclear power reactors (see Types of Nuclear Power Reactors).

Nuclear Power Reactors

There are many different types of power reactors. What is common to them all is that they produce thermal energy that can be used for its own sake or converted into mechanical energy and ultimately, in the vast majority of cases, into electrical energy.

In these reactors, the fission of heavy atomic nuclei, the most common of which is uranium-235, produces heat that is transferred to a fluid which acts as a coolant. During the fission process, bond energy is released and this first becomes noticeable as the kinetic energy of the fission products generated and that of the neutrons being released. Since these particles undergo intense deceleration in the solid nuclear fuel, the kinetic energy turns into heat energy.

In the case of reactors designed to generate electricity, to which the explanations below will now be restricted, the heated fluid can be gas, water or a liquid metal. The heat stored by the fluid is then used either directly (in the case of gas) or indirectly (in the case of water and liquid metals) to generate steam. The heated gas or the steam is then fed into a turbine driving an alternator.

Since, according to the laws of nature, heat cannot fully be converted into another form of energy, some of the heat is residual and is released into the environment. Releasing is either direct e.g. into a river or indirect, into the atmosphere via cooling towers. This practice is common to all thermal plants and is by no means limited to nuclear reactors which are only one type of thermal plant.

Types of Nuclear Power Reactors

Nuclear power reactors can be classified according to the type of fuel they use to generate heat.

Uraniumfuelled Reactors

The only natural element currently used for nuclear fission in reactors is uranium. Natural uranium is a highly energetic substance: one kilogram of it can generate as much energy as 10 tonnes of oil. Naturally occurring uranium comprises, almost entirely, two isotopes: U238 (99.283%) and U235 (0.711%). The former is not fissionable while the latter can be fissioned by thermal (i.e. slow) neutrons. As the neutrons emitted in a fission reaction are fast, reactors using U235 as fuel must have a means of slowing down these neutrons before they escape from the fuel. This function is performed by what is called a moderator, which, in the case of certain reactors (see table of Reactor Types below) simultaneously acts as a coolant. It is common practice to classify power reactors according to the nature of the coolant and the moderator plus, as the need may arise, other design characteristics.

Reactor Type

Coolant

Moderator

Fuel

Comment

Pressurised water reactors (PWR, VVER)

Light water

Light water

Enriched uranium

Steam gener-ated in secondary loop

Boiling water reactors (BWR)

Light water

Light water

Enriched uranium

Steam from boiling water fed to turbine

Pressurised heavy water reactor (PHWR)

Heavy water

Heavy water

Natural uranium

Gas-cooled reactors (Magnox, AGR, UNGG)

CO2

Graphite

Natural or enriched uranium

Light water graphite reactors (RBMK)

Press-urised boiling water

Graphite

Enriched uranium

Soviet design

PWRs and BWRs are the most commonly operated reactors in Organisation for Economic Cooperation and Development (OECD) countries. VVERs, designed in the former Soviet Union, are based on the same principles as PWRs. They use light water, i.e. regular water (H2O) as opposed to heavy water (deuterium oxide D2O). Moderation provided by light water is not sufficiently effective to permit the use of natural uranium. The fuel must be slightly enriched in U235 to make up for the losses of neutrons occurring during the chain reaction. On the other hand, heavy water is such an effective moderator that the chain reaction can be sustained without having to enrich the uranium. This combination of natural uranium and heavy water is used in PHWRs, which are found in a number of countries, including Canada, Korea, Romania and India.

Graphite-moderated, gas-cooled reactors, formerly operated in France and still operated in Great Britain, are not built any more in spite of some advantages.

RBMK-reactors (pressure-tube boiling-water reactors), which are cooled with light water and moderated with graphite, are now less commonly operated in some former Soviet Union bloc countries. Following the Chernobyl accident (26 April 1986) the construction of this reactor type ceased. The operating period of those units still in operation will be shortened.

Plutonium-fuelled Reactors

Plutonium (Pu) is an artificial element produced in uranium-fuelled reactors as a by-product of the chain reaction. It is one hundred times more energetic than natural uranium; one gram of Pu can generate as much energy as one tonne of oil. As it needs fast neutrons in order to fission, moderating materials must be avoided to sustain the chain reaction in the best conditions. The current Plutonium-fuelled reactors, also called fast reactors, use liquid sodium which displays excellent thermal properties without adversely affecting the chain reaction. These types of reactors are in operation in France, Japan and the Commonwealth of Independent States (CIS).

Light Water Reactors

The Light Water Reactors category comprises pressurised water reactors (PWR, VVER) and boiling water reactors (BWR). Both of these use light water and hence enriched uranium. The light water they use combines the functions of moderator and coolant. This water flows through the reactor core, a zone containing a large array of fuel rods where it picks up the heat generated by the fission of the U235 present in the fuel rods. After the coolant has transferred the heat it has collected to a steam turbine, it is sent back to the reactor core, thus flowing in a loop, also called a primary circuit.

In order to transfer high-quality thermal energy to the turbine, it is necessary to reach temperatures of about 300 C. It is the pressure at which the coolant flows through the reactor core that makes the distinction between PWRs and BWRs.In PWRs, the pressure imparted to the coolant is sufficiently high to prevent it from boiling. The heat drawn from the fuel is transferred to the water of a secondary circuit through heat exchangers. The water of the secondary circuit is transformed into steam, which is fed into a turbine.

In BWRs, the pressure imparted to the coolant is sufficiently lower than in a PWR to allow it to boil. It is the steam resulting from this process that is fed into the turbine.This basic difference between pressurised and boiling water dictates many of the design characteristics of the two types of light water reactors, as will be explained below.

Despite their differing designs, it must be noted that the two reactor types provide an equivalent level of safety.

Pressurised Water Reactors

The fission zone (fuel elements) is contained in a reactor pressure vessel under a pressure of 150 to 160 bar (15 to 16 MPa). The primary circuit connects the reactor pressure vessel to heat exchangers. The secondary side of these heat exchangers is at a pressure of about 60 bar (6 MPa) - low enough to allow the secondary water to boil. The heat exchangers are, therefore, actually steam generators. Via the secondary circuit, the steam is routed to a turbine driving an alternator. The steam coming out of the turbine is converted back into water by a condenser after having delivered a large amount of its energy to the turbine. It then returns to the steam generator. As the water driving the turbine (secondary circuit) is physically separated from the water used as reactor coolant (primary circuit), the turbine-alternator set can be housed in a turbine hall outside the reactor building.

Nuclear power plant with pressurized water reactor

Boiling Water Reactors

The fission zone is contained in a reactor pressure vessel, at a pressure of about 70 bar (7 MPa). At the temperature reached (290 C approximately), the water starts boiling and the resulting steam is produced directly in the reactor pressure vessel. After the separation of steam and water in the upper part of the reactor pressure vessel, the steam is routed directly to a turbine driving an alternator.

The steam coming out of the turbine is converted back into water by a condenser after having delivered a large amount of its energy to the turbine. It is then fed back into the primary cooling circuit where it absorbs new heat in the fission zone.

Since the steam produced in the fission zone is slightly radioactive, mainly due to short-lived activation products, the turbine is housed in the same reinforced building as the reactor.

Principle of a nuclear power plant with boiling water reactor

Question: Gravitational force

Gravity

Gravity is the weakest of the four fundamental forces, yet it is the dominant force in the universe for shaping the large scale structure of galaxies, stars, etc. The gravitational force between two masses m1 and m2 is given by the relationship:

This is often called the "universal law of gravitation" and G the universal gravitation constant. It is an example of an inverse square law force. The force is always attractive and acts along the line joining the centers of mass of the two masses. The forces on the two masses are equal in size but opposite in direction, obeying Newton's third law. Viewed as an exchange force, the massless exchange particle is called the graviton.

The gravity force has the same form as Coulomb's law for the forces between electric charges, i.e., it is an inverse square law force which depends upon the product of the two interacting sources. This led Einstein to start with the electromagnetic force and gravity as the first attempt to demonstrate the unification of the fundamental forces. It turns out that this was the wrong place to start, and that gravity will be the last of the forces to unify with the other three forces. Electroweak unification (unification of the electromagnetic and weak forces) was demonstrated in 1983, a result which could not be anticipated in the time of Einstein's search. It now appears that the common form of the gravity and electromagnetic forces arises from the fact that each of them involves an exchange particle of zero mass, not because of an inherent symmetry which would make them easy to unify.

gravitational force - (physics) the force of attraction between all masses in the universe; especially the attraction of the earth's mass for bodies near its surface; "the more remote the body the less the gravity"; "the gravitation between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them"; "gravitation cannot

Question: Kinetic energy

Kenetic energy = mv2, Momemntum =mv

Question: Temperature conversion- degree, faregnhit and kelvin

00C = 273K, Temperature in degree Celciuc = (Temperature in Farenhight -32) 5/9

Temperature in degree Celciuc = (Temperature in Farenhight -32) 5/9

= (104 -32)5/9= 72x 5/9 =40 degree celcius

Question: Series and parralel resistance, Power

In series resistances are added R= r1 + r2

In parallel 1/R = 1/r1 +1/r2

Power in the resistive circuit P =VI=I2R=V2/R

Question: heat required to melt ice falling from height

Heat Required to Melt a Solid

The heat required to melt a solid can be calculated as

q = Lm m (1)

where

q = required heat (J, Btu)

Lm = latent heat of melting (J/kg, Btu/lb)

m = mass of subsance (kg, lb)

If Ice fall the work done by ice in falling =mgh and then same is converted into heat for melting the amount of ice.

Example - Required Heat to melt Ice (Water)

The heat required to melt 10 kg of water can be calculated as

q = Lmm

= 334 103 (J/kg) 10 (kg)

= 3340000(J)

= 3340(kJ)

Chemistry

Question: Isomers

Compounds that have the same molecular formula but different chemical structures are called isomers. Remember isomerism is a property between a pair (or more) of molecules, i.e. a molecule is an isomer of another molecule.

Question: ore of aluminium

Bauxite is main ore of aluminium. It also occurs in the minerals beryl, cryolite, garnet, spinel and turquoise. Impurities in Al2O3, such as chromium or iron yield the gemstones ruby and sapphire, respectively.

In the Earth's crust, aluminium is the most abundant (8.3% by weight) metallic element and the third most abundant of all elements (after oxygen and silicon).[15] Because of its strong affinity to oxygen, it is almost never found in the elemental state; instead it is found in oxides or silicates. Feldspars, the most common group of minerals in the Earth's crust, are aluminosilicates. Native aluminium metal can only be found as a minor phase in low oxygen fugacity environments, such as the interiors of certain volcanoes.[16] Native aluminium has been reported in cold seeps in the northeastern continental slope of the South China Sea and Chen et al. (2011)[17] have proposed a theory of its origin as resulting by reduction from tetrahydroxoaluminate Al(OH)4 to metallic aluminium by bacteria.

Question: Maximum density gas

A mole of a gas has same volume under same volume so gas with highest mol. wt. has greatest mass/volume (density). Mol. wt. He = 4 Cl2 = 35.5*2 = 71 CH4 = 12+4*1 = 16 NH3 = 14+3*1 = 15

Similarly mol. Weight of O2 = 16x2=32

Mol weight of N2= 14x2 =28

Therefore the clorine gas which has highest molar weight therefore it has highest density.

Question: Amphoteric oxide

Amphoteric Substance

An amphoteric substance is one which has both acidic and basic properties and which can behave as a weak base or a weak acid under different experimental conditions.

Amphoteric Oxides

Amphoteric oxides are the oxides of weakly electropositive metals. Thus, the oxides of aluminium oxide, zinc oxide, and tin oxide are amphoteric oxides. These amphoteric oxides react as basic oxides with acids and as acidic oxides with bases.

Aluminium oxide reacts with acids

Al2O3 + 6 HCl ==> 2 AlCl3 + 3 H2O

Aluminium oxide reacts with bases

Al2O3 + 2 NaOH + H2O ==>2 NaAl(OH)4

Water is also an amphoteric oxide

H2O + NH3 NH4(+) + OH(-)

H2O + HCl H3O(+) + Cl(-)

Question: Alloy of steel and other alloy

Alloys of Iron

A number of steels are the important alloys of iron, which include, Steel Stainless Steel Chromium Steel Tungsten Steel

Alloy

An alloy is a solid solution of one metal in another. It is an example of a mixture, as no chemical bonding exists between the constituent elements in the alloy.

Common examples of alloys include

Brass (an alloy of copper and zinc, and sometimes other metals, known since Roman Times and widely used in industry, for ornament and decoration ),

Bronze (an alloy of copper and Tin used for tools, weapons, machine parts and marine hardware),

Stainless steel (an alloy of iron, chromium and nickel used for cutlery and industrial components where corrosion resistance is required),

Duralium (an alloy of aluminium, copper, magnesium, manganese and silicon used in aircraft construction) and

Solder (an alloy of lead and tin used in making electrical connections).

Allotrope

An allotrope of an element is one of the forms in which the element can exist.

For example, carbon can exist in several different forms, including graphite and diamond (which are pure forms of carbon that have different crystal structures) and charcoal, coke and lampblack (which are impure forms of carbon that are amorphous).

Sulphur can exist as five different allotropes and they are S2, S3, S4 (DISULPHUR, TRISULPHUR, TETRA SULPHUR)

Question: Acid and base

Acid

An Acid is defined as a substance which contains hydrogen that can be displaced by a metal with the liberation of hydrogen gas and the formation of a salt.

An understanding of the chemical mechanisms that give rise to the properties of acids evolved from a number of different theories of the nature of acids.

Arrhenius proposed the Arrhenius Concept of Bases that an acid is a substance which provides hydrogen ions as a result of dissociation and ionization in aqueous solution.

Lewis proposed the Lewis Theory of Acids that there is a reciprocal relationship between acids and bases, and he introduced the concept of Lewis Conjugate Acid-Base Pairs.

Bronsted and Lowry proposed the Bronsted Lowry Theory of Acids that acids are proton donors and that bases are proton acceptors.

Question: 4g of clacium react with HCL to form molecules of H2

Ca + 2HCl = CaCl2 + H2

1 mole of ca required for one mole of H2

Therefore number of moles n = mass(m)/Molar mass = 4/40=0.1 for Calcium

For Hydrogen n = 0.1

Molecules of hydrogen = 0.1x 6.02 x 1023= 6.02x 1022

Question: Anealing

Annealing is a heat process whereby a metal is heated to a specific temperature /colour and then allowed to cool slowly. This softens the metal which means it can be cut and shaped more easily. Mild steel, is heated to a red heat and allowed to cool slowly. However, metals such as aluminium will melt if heated for too long.

PHYSICAL PROPERTIES: Annealed metals are relatively soft and can be cut and shaped more easily. They bend easily when pressure is applied. As a rule they are heated and allowed to cool slowly.

PHYSICAL PROPERTIES: Hardened metals are difficult to cut and shape. They are very difficult if not impossible to bend. As a rule they are heated and cooled very quickly by quenching in clean, cold water.

Question: Which substances which acts as both oxidizing and reducing agents

Any substance containing an atom that it is at an intermediate oxidation level compared to all its possible oxidation states. For example in hydrogen peroxide (H2O2) oxygen is at the -1 state. However oxygen can be also at 0 or -2. Thus under proper conditions H2O2 acts a reducing agent and thus it oxidises to O2 (0 oxidation number) or as an oxidising agent and thus it gets reduced to O with an oxidation number -2

Hydrogen gas is a reducing agent when it reacts with non-metals and an oxidising agent when it reacts with metals. Oxidising agent: 2Li(s) + H2(g) -->2LiH(s) hydrogen acts as an oxidizing agent because it accepts an electron donation from lithium, which causes Li to be oxidized. Reducing agent: H2(g) + F2(g) --> 2HF(g) hydrogen acts as a reducing agent because it donates its electrons to fluorine, which allows fluorine to be reduced.

Question: Isotones

isotone, any of two or more species of atoms or nuclei that have the same number of neutrons. Thus, chlorine-37 and potassium-39 are isotones, because the nucleus of this species of chlorine consists of 17 protons and 20 neutrons, whereas the nucleus of this species of potassium contains 19 protons and 20 neutrons.

Question: Reagents

Reagents are "substances or compounds that are added to a system in order to bring about a chemical reaction or are added to see if a reaction occurs."[1] Some reagents are just a single element. However, most processes require reagents made of chemical compounds.

Question: Trend in periodic table

Periodic TrendsTable of Contents

1. 1. Electronegativity Trends

2. 2. Ionization Energy Trends

3. 3. Electron Affinity Trends

4. 4. Atomic Radius Trends

5. 5. Melting Point Trends

6. 6. Metallic Character Trends

7. 7. Outside Links

8. 8. Problems

9. 9. Solutions

10. 10. References

11. 11. Contributors

Periodic trends are specific patterns that are present in the periodic table, which illustrate different aspects of a certain element, including its size and its properties with electrons. The main periodic trends include: electronegativity, ionization energy, electron affinity, atomic radius, melting point, and metallic character. The periodic trends that arise from the arrangement of the periodic table provide chemists with an invaluable tool to quickly predict an element's properties. These trends exist because of the similar atomic structure of the elements within their respective group families or period and the periodic nature of the elements.

Electronegativity Trends

Electronegativity can be understood as chemical property describing an atom's ability to attract and bind to electrons. Because electronegativity is a qualitative property, there is not a standardized method for calculating electronegativity. However, the scale that most chemists use in quantifying electronegativity is the Pauling Scale, named after the chemist Linus Pauling. The numbers assigned by the Pauling scale are dimensionless due to electronegativity being largely qualitative. Electronegativity values for each element can be found on certain periodic tables. An example is provided below.

Figure 1. Periodic Table of Electronegativity values

Electronegativity measures an atom's strength to attract and form bonds with electrons. This property exists due to the electronic configuration of atoms. Most atoms prefer to fulfilling the octet rule (having the valence, or outer, shell comprise of 8 electrons). Since elements on the left side of the periodic table have less than a half-full valence shell, the energy required to gain electrons is significantly higher compared to the energy required to lose electrons. As a result, the elements on the left side of the periodic table generally lose electrons in forming bonds. Conversely, elements on the right side of the periodic table are more energy-efficient in gaining electrons to create a complete valence shell of 8 electrons. This effectively describes the nature of electronegativity: the more inclined an atom is to gain electrons, the more likely that atom will pull electrons toward itself.

As you move to the right across a period of elements, electronegativity increases. When the valence shell of an atom is less than half full, it requires less energy to lose an electron than gain one and thus, it is easier to lose an electron. Conversely, when the valence shell is more than half full, it is easier to pull an electron into the valence shell than to donate one.

As you move down a group, electronegativity decreases. This is because the atomic number increases down a group and thus there is an increased distance between the valence electrons and nucleus, or a greater atomic radius.

Important exceptions of the above rules include the noble gases, lanthanides, and actinides. The noble gases possess a complete valence shell and do not usually attract electrons. The lanthanides and actinides possess a more complicated chemistry that does not generally follow any trends. Therefore, noble gases, lanthanides, and actinides do not have electronegativity values.

As for the transition metals, while they have values, there is little variance among them as you move across the period and up and down a group. This is because of their metallic properties that affect their ability to attract electrons as easily as the other elements.

With these two general trends in mind, we can deduce that the most electronegative element is fluorine, which weighs in at a hefty 3.98 Pauling units.

Figure 2. Periodic Table showing Electronegativity Trend

Ionization Energy Trends

Ionization Energy is the amount of energy required to remove an electron from a neutral atom in its gaseous phase. Conceptually, ionization energy is considered the opposite of electronegativity. The lower this energy is, the more readily the atom becomes a cation. Therefore, the higher this energy is, the more unlikely the atom becomes a cation. Generally, elements on the right side of the periodic table have a higher ionization energy because their valence shell is nearly filled. Elements on the left side of the periodic table have low ionization energies because of their willingness to lose electrons and become cations. Thus, ionization energy increases from left to right on the periodic table.

Another factor that affects ionization energy is electron shielding. Electron shielding describes the ability of an atom's inner electrons to shield its positively-charged nucleus from its valence electrons. When moving to the right on a period of elements, the number of electrons increases and the strength of shielding increases. As a result, it is easier for valence shell electrons to ionize and thus the ionization energy decreases when going down a group. In certain texts, electron shielding may also be known as screening.

The ionization energy of the elements within a period generally increases from left to right. This is due to valence shell stability.

The ionization energy of the elements within a group generally decreases from top to bottom. This is due to electron shielding.

The noble gases possess very high ionization energies because of their full valence shell as indicated in the graph. Note that Helium has the highest ionization energy of all the elements.

Figure 3. Graph showing the Ionization Energy of the Elements from Hydrogen to Argon

Some elements can have several ionization energies, so we refer to these varying energies as the first ionization energy, the second ionization energy, third ionization energy, etc. The first ionization energy is to the energy needed to remove the outermost, or highest, energy electron and the second ionization energy is the energy required to remove any subsequent high-energy electron from a gaseous cation. Below are the formulas for calculating the first and second ionization energies.

First Ionization Energy:

X(g)X+(g)+e

Second Ionization Energy:

X+(g)X2+(g)+e

Generally, any subsequent ionization energies (2nd, 3rd, etc.) follow the same periodic trend as the first ionization energy.

Figure 4. Periodic Table Showing Ionization Energy Trend

Ionization energies decrease as atomic radii increase. This observation is affected by n (the principle quantum number) and Zeff (based on the atomic number and shows how many protons are seen in the atom) on the ionization energy (I). Given by the following equation:

I=RHZ2eff/n2

Going across a period, the Zeffincreases and n (principal quantum number) remains the same, so that the ionization energy increases.

Going down a group, the n increases and Zeffincreases slightly, the ionization energy decreases.

Electron Affinity Trends

Like the name suggests, electron affinity describes the ability of an atom to accept an electron. Unlike electronegativity, electron affinity is a quantitative measure that measures the energy change that occurs when an electron is added to a neutral gas atom. When measuring electron affinity, the more negative the value, the more of an affinity to electrons that atom has.

Electron affinity generally decreases down a group of elements because each atom is larger than the atom above it (this is the atomic radius trend, which will be discussed later in this text). This means that an added electron is further away from the atom's nucleus compared to its position in the smaller atom. With a larger distance between the negatively-charged electron and the positively-charged nucleus, the force of attraction is relatively weaker. Therefore, electron affinity decreases. Moving from left to right across a period, atoms become smaller as the forces of attraction become stronger. This causes the electron to move closer to the nucleus, thus increasing the electron affinity from left to right across a period.

Electron affinity increases from left to right within a period. This is caused by the decrease in atomic radius.

Electron affinity decreases from top to bottom within a group. This is caused by the increase in atomic radius.

Figure 5. Periodic Table showing Electron Affinity Trend

Atomic Radius Trends

For atoms, the atomic radius is one-half the distance between the nuclei of two atoms is (just like a radius is half the diameter of a circle). However, this idea is complicated by the fact that not all atoms are normally bound together in the same way. Some are bound by covalent bonds in molecules, some are attracted to each other in ionic crystals, and others are held in metallic crystals. Nevertheless, it is possible for a vast majority of elements to form covalent molecules in which two like atoms are held together by a single covalent bond. The covalent radius of these molecules is often referred to as the atomic radius. This distance is measured in picometers. Going through each of the elements of the periodic table, patterns of the atomic radius can be seen.

Atomic size gradually decreases from left to right across a period of elements. This is because, within a period or family of elements, all electrons are being added to the same shell. But, at the same time, protons are being added to the nucleus, making it more positively charged. The effect of increasing proton number is greater than that of the increasing electron number; therefore, there is a greater nuclear attraction. This means that the nucleus attracts the electrons more strongly, having the atom's shell pulled closer to the nucleus. The valence electrons are held closer towards the nucleus of the atom. As a result, the atomic radius decreases.

Going down a group, it can be seen that atomic radius increases. The valence electrons occupy higher levels due to the increasing quantum number (n). As a result, the valence electrons are further away from the nucleus as the n increases. Electron shielding prevents these outer electrons from being attracted to the nucleus; thus, they are loosely held and the resulting atomic radius is large.

Atomic radius decreases from left to right within a period. This is caused by the increase in the number of protons and electrons across a period. One proton has a greater effect than one electron; thus, a lot of electrons will get pulled towards the nucleus, resulting in a smaller radius.

Atomic radius increases from top to bottom within a group. This is caused by electron shielding.

Figure 6. Periodic Table showing Atomic Radius Trend

Melting Point Trends

Melting points are the amount of energy required to break a bond(s) to change the solid phase of a substance to a liquid. Generally, the stronger the bond between the atoms of an element, the higher the energy requirement in breaking that bond. Since temperature is directly proportional to energy, high bond dissociation energy correlates to a high temperature. Melting points are varied and don't generally form a distinguishable trend across the periodic table. However, certain conclusions can be drawn from the following graph.

Metals generally possess a high melting point.

Most non-metals possess low melting points.

The non-metal carbon possesses the highest boiling point of all the elements. The semi-metal boron also possesses a high melting point.

Figure 7. Chart of Melting Points of Various Elements

Metallic Character Trends

The metallic character of an element can be defined as how readily an atom can lose an electron. As you move from right to left across a period, metallic character increases because the attraction between valence electron and the nucleus is weaker, thus enabling an easier loss of electrons. Metallic character increases as you move down a group because the atomic size is increasing. When the atomic size increases, the outer shells are farther away.The principle quantum number increases and average electron density moves farther from nucleus. The electrons of the valence shell have less of an attraction to the nucleus and, as a result, can lose electrons more readily, causing an increase in metallic character.

Metallic characteristics decrease from left to right across a period. This is caused by the decrease in radius (above it is stated that Zeff causes this)of the atom which allows the outer electrons to ionize more readily.

Metallic characteristics increase down a group. Electron shielding causes the atomic radius to increase thus the outer electrons ionizes more readily than electrons in smaller atoms.

Metallic character relates to the ability to lose electrons, and nonmetallic character relates to the ability to gain electrons.

Another easier way to remember the trend of metallic character is that as you move from left and down towards the bottom-left corner of the periodic table, metallic character increases because you are heading towards Groups 1 and 2, or the Alkali and Alkaline metal groups. Likewise, if you move up and to the right to the upper-right corner of the periodic table, metallic character decreases because you are passing by to the right side of the staircase, which indicate the nonmetals. These include the Group 8, the noble gases, and other common gases such as oxygen and nitrogen.

In other words:

Move left across period and down the group: increase metallic character (heading towards alkali and alkaline metals)

Move right across period and up the group: decrease metallic character (heading towards nonmetals like noble gases)

Figure 8. Periodic Table of Metallic Character Trend

Problems

The following series of problems will review your general understanding of the aforementioned material.

1.) Based on the periodic trends for ionization energy, which do you expect to have the highest ionization energy?

1. A.) Fluorine (F)

2. B.) Nitrogen (N)

3. C.) Helium (He)

2.) Nitrogen has a larger atomic radius than Oxygen.

1. A.) True

2. B.) False

3.) Which do you expect to have more metallic character, Lead (Pb) or Tin(Sn)?

4.) Which element do you expect to have the higher melting point: chlorine (Cl) or bromine (Br)?

5.) Which element do you expect to be more electronegative, sulfur (S) or selenium (Se)?

6) Why is the electronegativity value of most noble gases equal to zero?

7) Arrange these atoms in accordance to decreasing effective nuclear charge by the valence electrons: Si, Al, Mg, S

8) Rewrite the following list in order of decreasing electron affinity: Fluorine (F), Phosphorous (P), Sulfur (S), Boron (B).

9) An atom with an atomic radius smaller than that of Sulfur (S) is __________.

1. A.) Oxygen (O)

2. B.) Chlorine (Cl)

3. C.) Calcium (Ca)

4. D.) Lithium (Li)

5. E.) None of the above

10) A nonmetal will have a smaller ionic radius when compared to a metal of the same period.

1. A.) True B.) False

11) Which one of the following has the lowest first ionization energy?

1. A. Element A

2. B. Element B

3. C. Element C

4. D. Element D

Question: Carborundum

Silicon carbide (SiC), also known as carborundum /krbrndm/, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite,

In the arts, silicon carbide is a popular abrasive in modern lapidary due to the durability and low cost of the material. In manufacturing, it is used for its hardness in abrasive machining processes such as grinding, honing, water-jet cutting and sandblasting. Particles of silicon carbide are laminated to paper to create sandpapers and the grip tape on skateboards.[3

Silicon carbide is used as a support and shelving material in high temperature kilns such as for firing ceramics, glass fusing, or glass casting. SiC kiln shelves are considerably lighter and more durable than traditional alumina shelves.

Gapped SiC lightning arresters were used as lightning-protection tool and sold under GE and Westinghouse brand names, among others. The gapped SiC arrester has been largely displaced by no-gap varistors that use columns of zinc oxide pellets.[40]

SiC is still one of the important LED components it is a popular substrate for growing GaN devices, and it also serves as a heat spreader in high-power LEDs.

SIC also used in astronomy, thin filament pyrometry, heating element, nuclear fuel particle, Nuclear fuel cladding, jewelary, steel production, catalyst support carborundum print making and graphene production.

Question: Freon

A chlorofluorocarbon (CFC) is an organic compound that contains only carbon, chlorine, and fluorine, produced as a volatile derivative of methane and ethane. They are also commonly known by the DuPont brand name Freon. The most common representative is dichlorodifluoromethane (R-12 or Freon-12). Many CFCs have been widely used as refrigerants, propellants (in aerosol applications), and solvents. The manufacture of such compounds has been phased out (and replaced with products such as R-410A) by the Montreal Protocol because they contribute to ozone depletion in the upper atmosphere.

The most important reaction of the CFCs is the photo-induced scission of a C-Cl bond:

CCl3F CCl2F. + Cl.

The chlorine atom, written often as Cl., behaves very differently from the chlorine molecule (Cl2). The radical Cl. is long-lived in the upper atmosphere, where it catalyzes the conversion of ozone into O2. Ozone absorbs UV-B radiation, so its depletion allows more of this high energy radiation to reach the Earth's surface. Bromine atoms are even more efficient catalysts, hence brominated CFCs are also regulated.

Question: Permanent hardness in water

Permanent hardness stalna tvrdoa

Permanent hardness in water is hardness due to the presence of the chlorides, nitrates and sulphates of calcium and magnesium, which will not be precipitated by boiling. The lime scale can build up on the inside of the pipe restricting the flow of water or causing a blockage. This can happen in industry where hot water is used.

Temporary Hardness is due to the bicarbonate ion, HCO3-, being present in the water. This type of hardness can be removed by boiling the water to expel the CO2, as indicated by the following equation:

Ca(HCO3)2 CaCO3 + CO2 + H2O

Permanent hardness is due to calcium and magnesium nitrates, sulphates, and chlorides etc. This type of hardness cannot be eliminated by boiling.

Brinell hardness Brinellova tvrdoa

Brinell hardness is a scale for measuring the hardness of metals introduced around 1900 by Swedish metallurgist Johan Brinell (1849-1925). A small chromium steel ball is pressed into the surface of the metal by a load of known weight. The loading force is in the range of 300N to 30000N. The ratio of the mass of the load in kilograms to the area of the depression formed in square millimetres is the Brinell Hardness Number.

18.3.1 - State and explain whether salts form acidic, alkaline or neutral aqueous solutions. Examples should include salts formed from the four possible combinations of strong and weak acids and bases. The effect of the charge density of the cations in groups 1, 2, 3 and d-block elements should also be considered, eg [Fe(H2O)6]3+ [Fe(OH)(H2O)5]2+ + H+ .

Question: Which of these salts will not suffer hydrolysis

Usually hydrolysis is a chemical process in which a molecule of water is added to a substance. Sometimes this addition causes both substance and water molecule to split into two parts. In such reactions, one fragment of the target molecule (or parent molecule) gains a hydrogen ion.

Salt hydrolysis

Salts are ionic, this means that they dissociate 100% in solution to give free aqueous ions

NaCl Na+ + Cl-

When both ions come from strong acid and bases they have no interactions with the ions formed by the dissociation of water (hydrogen and hydroxide ions), however if the ions come from weak acids and bases then they interact with the ions from water establishing equilibria.

Hence salts of ethanoic acid produce free ethanoate ions in solution that can interact with the hydrogen ions from the water.

Example: Sodium ethanoate solution

sodium ethanoate is 100% dissociated into ions:-

CH3COONa CH3COO- + Na+

Sodium ions are from a strong base (sodium hydroxide) and do not interact with the water ions.

However, the ethanoate ions do interact with the hydrogen ions from the water equilibrium (H2O H+ + OH-)

CH3COO- + H+ CH3COOH

We know that this last equilibrium lies to the side of the ethanoic acid (to the right), removing the hydrogen ions from the solution. As [H+] decreases the pH rises.

Hence a solution of sodium ethanoate has a pH greater than 7. We say that it is basic by hydrolysis.

Example: Ammonium chloride solution

Ammonium chloride dissociates 100% into ions in solution

NH4Cl NH4+ + Cl-

The ammonium ions interact with the hydroxide ions from the water removing them from the solution (equilibrium lies to the right)

NH4+ + OH- NH3 + H2O

This increases the concentration of hydrogen ions (as [H+] x [OH-] is constant) increasing the acidity of the solution (decrease pH)

We say that a solution of ammonium chloride is acidic by hydrolysis.

General rules

When the negative ion is from a weak acid then the salt is basic by hydrolysis

When the positive ion is from a weak base then the salt is acidic by hydrolysis

If the salt is formed from a strong acid and strong base then it is neutral

If the salt is formed from a weak acid and weak base then its hydrolysis is determined by the relative Ka and Kb values

Salts involving ions with a high charge density

Solvation

Ionic compounds dissociate 100% into ions in solution. These ions become solvated by the water molecules (the water molecules bond to the ions - this is one of the driving forces behind dissolution). The polar water molecules use the lone pairs on the oxygen of the water to coordinate to the positive metal ion. The ions are then enclosed by a 'cage' of water molecules usually in an octahedral arrangement.

Octahedral arrangement of water molecules around a positive ion (in this case a 3+ ion)

Charge density

This means the charge to size ratio of the ion.

charge density = ionic charge/ionic size

When the ion has a charge of 3+ or when it is very small this charge to size ratio is enough to polarise the water molecules surrounding the ion in solution. This results in a weakening of the O-H bonds within the water molecules allowing hydrogen ions to be released into the solution. Hence the solutions are acidic.

This effect is typified in aluminium salts (the aluminium ion has a charge of 3+) which are very acidic in solution

The aluminium hexaaqua ion

Aluminium ions are surrounded by six water molecules in an octahedral arrangement. This is called the aluminium hexaaqua ion. The high charge density of the aluminium ion polarises the water molecules and hydrogen ions are released into solution. The solution is so acidic that it releases carbon dioxide from sodium carbonate (this reaction is used in some fire extinguishers to produce foam in conjunction with detergent)

[Al(H2O)6]3+ [Al(OH)(H2O)5]2+ + H+[Al(OH)(H2O)5]2+ [Al(OH)2(H2O)4]+ + H+

Transition metals

As the transition metals have variable oxidation states the ions that are formed with high charges (high oxidation state) also produce acidic solutions. A good examle of this is the Iron III ion. Salts such as iron III sulphate are acidic in solution.

[Fe(H2O)6]3+ [Fe(OH)(H2O)5]2+ + H+

Question: How many atoms present in 4g of NaOH

First put your grams into moles: 4g NaOH x 1 mol NaOH/ 39.99g (molar mass) NaOH = 0.1 mol NaOH *Note: unit of grams cancel* Then find the number of molecules using Avogadro's number: 0.1 mol NaOH x 6.02 x 10^23 molecules NaOH/ 1 mol NaOH *Note: unit of moles cancel* = 6.02 x 10^22 molecules NaOH

There three atoms in NaOH therefore Numbers of atoms in NaOH = 3 x 6.02 x 1022=1.8 x 1023

Question: Concentration of (H+) in water is 10-4M. This shows that pH is

We could describe the relative strengths of dilute solutions of acids and bases by listing the molarity of H+ for acidic solutions and the molarity of OH- for basic solutions. There are two reasons why we use the pH scale instead. The first reason is that instead of describing acidic solutions with [H+] and basic solutions with [OH-], chemists prefer to have one scale for describing both acidic and basic solutions. Because the product of the H+ and OH- concentrations in such solutions is always 1.01 10-14 at 25 C, when we give the concentration of H+, we are indirectly also giving the concentration of OH-. For example, when we say that the concentration of H+ in an acidic solution at 25 C is 10-3 M, we are indirectly saying that the concentration of OH- in this same solution is 10-11 M. When we say that the concentration of H+ in a basic solution at 25 C is 10-10 M, we are indirectly saying that the OH- concentration is 10-4 M. The pH concept makes use of this relationship to describe both dilute acid and dilute base solutions on a single scale.

The next reason for using the pH scale instead of H+ and OH- concentrations is that in dilute solutions, the concentration of H+ is small, leading to the inconvenience of measurements with many decimal places, such as 0.000001 M H+, or to the potential confusion associated with scientific notation, as with 1 10-6 M H+. In order to avoid such inconvenience and possible confusion, pH is defined as the negative logarithm of the H+ concentration.

pH = -log[H+]

Instead of saying that a solution is 0.0000010 M H+ (or 1.0 10-6 M H+) and 0.000000010 M OH- (or 1.0 10-8 M OH-), we can indirectly convey the same information by saying that the pH is 6.00.

pH = -log[H+] = -log(1.0 10-6) = 6.00

When taking the logarithm of a number, report the same number of decimal positions in the answer as you had significant figures in the original value. Because 1.0 10-6 has two significant figures, we report 6.00 as the pH for a solution with 1.0 10-6 M H+. The table below shows a range of pH values for dilute solutions of acid and base.

pH of Dilute Solutions of Acids and Bases at 25 C

[H+]

[OH-]

pH

1.0

1.0 10-14

0.00

1.0 10-1

1.0 10-13

1.00

1.0 10-2

1.0 10-12

2.00

1.0 10-3

1.0 10-11

3.00

1.0 10-4

1.0 10-10

4.00

1.0 10-5

1.0 10-9

5.00

1.0 10-6

1.0 10-8

6.00

1.0 10-7

1.0 10-7

7.00

1.0 10-8

1.0 10-6

8.00

1.0 10-9

1.0 10-5

9.00

1.0 10-10

1.0 10-4

10.00

1.0 10-11

1.0 10-3

11.00

1.0 10-12

1.0 10-2

12.00

1.0 10-13

1.0 10-1

13.00

1.0 10-14

1.0

14.00

Question: 8 g of gas occupies 5.6 liter at NTP. This shows molecular weight of the gas is

8/moleculat wieght = 5.6/22.4

Molecular wieght of gas is 8 x 22.4/5.6 = 32

1. Calculate the number of moles of each gas that are present for each. Give volume at STP.

a) 8 liters of N2

x = = .36 moles

b) 134.4 liters of H2

x = = 6 moles

c) 5.6 liters of CO

x = = .25 moles

d) 67.2 liters of N2O4

x = = 3 moles

e) 89,600ml of NO2

89,600ml= 89.6x = = 4 moles

2. Find the number of molecules present in exercises 1 a), b), and c).

a) N2

# N2 molecules = (.36 moles)(6 x 1023 molecules/mole)= 2.16 x 1023 molecules

b) H2

# H2 molecules = (6 moles)(6 x 1023 molecules/mole)= 36 x 1023 molecules = 3.6 x 1024 molecules

c) CO

# CO molecules = (.25 moles)(6 x 1023 molecules/mole)= 1.5 x 1023 molecules

3. Four moles of N2O5 gas will occupy what volume at STP.

x = = 89.6

4. 1.5 moles of NH3 gas will occupy what volume at STP.

x = = 33.6

5. How many grams of Cl2 gas are present in 11.2 liters of gas at STP?

x = = .5 molesMW Cl2 = 2(35.5) = 71 g/mole#g Cl2 = (MW)(moles) = (71 g/mole)(.5 moles) = 35.5g

6. How many grams of NH3 gas are present in 44.8 liters of the gas at STP?

x = = 2 molesMW NH3 = 14 + 3(1) = 17 g/mole#g NH3= (MW)(moles) = (17 g/mole)(2 moles) = 34g

7. 2.5g of a gas occupies 4 liters at STP. Find the molecular weight of the gas.

x = = 14g = MW

8. 1.25g of a gas occupies 2.5 liters at STP. Find the molecular weight of the gas.

x = = 11.2g = MW

9. A gas has a density of 1.75g/l at STP. Find its molecular weight.

x = = 39.2g = MW

10. A gas has a density of 2.75g/l at STP. Find its molecular weight.

x = = 61.6g = MW

11. Calculate the density of the following gases at STP:

a) SO2

MW SO2 = = 64 g/mole1 mole = 22.4D = 64g/22.4 = 2.9 g/

b) O3

MW = O3 = = 48 g/moleD = 48g/22.4 = 2.1 g/

c) PCl5

MW PCl5 = = 208.5 g/moleD = 208.5g/22.4 = 9.3 g/

12. Calculate the volume (in liters and milliliters) occupied by each of the following gases at STP:

a) 14g of N2

MW N2 = 2(14) = 28 g/molex = x = 11.2 = 11,200ml

b) 528g of UF6

MW UF6 = = 352 g/molex = x = 33.6 = 33,600ml

c) 90g of H2O

MW H2O = = 18 g/molex = x = 112 = 112,000ml

Question: Gas can not be liquified if it is

All real gases can be liquefied. Depending on the gas this might require compression and/or cooling. However, there exists for each gas a temperature above which the gas cannot be liquefied. This temperature, above which the gas cannot be liquefied, is called the critical temperature and it is usually symbolized by, TC . In order to liquefy a real gas the temperature must be at, or below, its critical temperature.

There are gases, sometimes called the "permanent gases" which have critical temperatures below room temperature. These gases must be cooled to a temperature below their critical point, which means below room temperture, before they can be liquefied. Examples of "permanent gases" include, He, H2, N2, O2, Ne, Ar, and so on. Many substances have critical temperatures above room temperature. These substances exist as liquids (or even solids) at room temperature. Water, for example, has a critical temperature of 647.1 K, much higher than the 298.15 K standard room temperature. Water can be liquefied at any temperature below 647.1 K (although above 398.15 - the normal boiling point of water - you would have to apply a pressure higher than atmospheric temperature in order to keep it liquid.

Question: 20 g of limestone after heating gave 4.4 g CO2. The % of CaCO3 in the is

CaCo3= CO2 + CaO

20/(40+12+48) n= 4.4/(12+32)

20/100n=4.4/44

1/5n=1/10

N=5/10=(5/10)x 100=50%

Question: H3PO4 + 2NaOH =Na2PO4 + 2H2O. Molecular weight of H3PO4 is 120. The equivalent weight of He3PO4 for the given reaction is

EQUIVALENT MASSES AND NORMALITY

All volumetric analysis problems can be solved in the usual manner, on the basis of the mole, molarsolutions and balanced chemical equations. There is however, another method, based on equivalents and normal solutions which does not require the use of any balanced chemical equations. In this method equivalents are used rather than moles. The definition of an equivalent is based on the fact that one equivalent of a given reactant will react with exactly one equivalent of another reactant.

There are two types of reactions for which equivalents are defined: (1) acid-base reactions and, (2) oxidation-reduction reactions. In CHEM 1110 we will deal with acid-base reactions. You will encounter equivalents for oxidation-reduction reactions next semester in CHEM 1210 (hopefully!!). For acid-base reactions, equivalent weights or equivalent masses are based on the fact that one H+(aq) ion reacts with one OH-(aq) ion. One equivalent of an acid is the mass of the acid that supplies one mole of H+(aq) ions, and one equivalent of a base is the amount of the base which supplies one mole of OH-(aq) ions. The equivalent weight or equivalent mass is therefore given by the general equation,

equivalent mass = molar mass/a where "a" for an acid is the number of moles of H+(aq) supplied by one mole of acid in the reaction taking place, and for a base "a" is the number of moles of OH-(aq) supplied by one mole of base in the reaction taking place.

EXAMPLES: (1) HCl + NaOH H NaCl + H2O

Equivalent mass HCl = Molar mass HCl = 36.5 g

Equivalent mass NaOH = Molar mass NaOH = 40.0 g

(2) H2SO4 + 2NaOH H Na2SO4 + 2H2O

Equivalent mass NaOH = Molar mass NaOH = 40.0 g

Equivalent mass H2SO4 = (Molar mass H2SO4)/2 = 49.0 g

(3) H3PO4 + 3NaOH H Na3PO4 + 3H2O

Equivalent mass NaOH = Molar mass NaOH = 40.0 g

Equivalent mass H3PO4 = (Molar mass H3PO4)/3= 32.7 g

(4) H3PO4 + 2NaOH H Na2HPO4 + 2H2O

Equivalent mass NaOH = Molar mass NaOH = 40.0 g

Equivalent mass H3PO4 = (Molar mass H3PO4)/2= 49.0 g

The concentration unit "normality, (N)" of a solution is the number of equivalents of solute dissolved in one liter of solution, that is Normality = (equivalents of solute)/Liter of solution

The concentration units of normality and molarity are related by the simple relationship:

N = aM -10-

NOTE: Since the number of H+(aq) per mole of acid and OH-(aq)per mole of base is at least one, the normality can never be smaller than the molarity; it must always be either the same as the molarity or a whole number multiple of the molarity.

EXAMPLES: (1) HCl + NaOH H NaCl + H2O

1.0 M HCl = 1.0 N HCl

(2) H2SO4 + 2NaOH H Na2SO4 + 2H2O

1.0 M H2SO4 = 2.0 N H2SO4

(3) H3PO4 + 3NaOH H Na3PO4 + 3H2O

1.0 M H3PO4 = 3.0 N H3PO4

(4) H3PO4 + 2NaOH H Na2HPO4 + 2H2O

1.0 M H3PO4 = 2.0 N H3PO4

Now that equivalent masses and normality have been discussed and shown to depend on the reaction between the acid and base, we can proceed to see how normality can be used in volumetric analysis.

From the definition of normality we can write:

# equivalents of A = (Volume of A)x(Normality of A)

At the equivalence point of an acid-base titration the equivalents of acid equals the equivalents of base: equivalents of acid = equivalents of base

VacidNacid = VbaseNbase

The use of normality this simplifies solution stoichiometry problems since a balanced chemical equation is not needed because the stoichiometric coefficients have already been accounted for by using equivalents instead of moles.

EXAMPLE: 10.0 mL of an unknown acid required 20.0 mL of 0.125 N NaOH to reach the equivalencepoint.

(a) Calculate the normality of the unknown acid.

(b) What is the molarity of the unknown acid if one mole of acid reacts two moles of base

in the neutalization process?

Answer: (a) equivalents of acid = equivalents of base

VacidNacid = VbaseNbase

Therefore Nacid = (20.0 mL)(0.125 N)/(10.0 mL) = 0.250 N

(b) Macid = 0.250 N/2 = 0.125 M

Notice that in solving this problem no use was made of any balanced chemical equation for the reaction between the acid and the base. The reason is that by making use of normality the stoichiometry is "built in".

-11-

QUESTIONS DEALING WITH EQUIVALENT MASSES AND NORMALITY

1. Calculate the equivalent mass of the triprotic acid, citric acid (C6H8O7).

2. Calculate the equivalent mass of aluminum hydroxide.

3. If 900.4 mg of the diprotic acid, oxalic acid (H2C2O4) is exactly neutralized by 24.10 mL of NaOH solution. Calculate the normality of the NaOH solution.

4. If 3.12 mmol of Bi(OH)3 are completely neutralized by 25.00 mL of H2SO4 solution. Calculate the normality and the molarity of the H2SO4 solution.

5. 294.0 mg of an unknown acid was neutralized by exactly 28.30 mL of 0.3180 N NaOH solution.

(a) Calculate the equivalent mass of the unknown acid.

(b) Calculate the molar mass of the unknown acid if it is monoprotic (i.e. HA).

(c) Calculate the molar mass of the unknown acid if it is diprotic (i.e. H2A).

(d) Calculate the molar mass of the unknown acid if it is triprotic (i.e. H3A).

ANSWERS TO ABOVE QUESTIONS

1. 64.05 g/equivalent

2. 26.00 g/equivalent

3. 0.8299 N

4. 0.3744 N and 0.1872 M

5. (a) 32.67 g/equivalent

(b) 32.67 g/mol

(c) 65.34 g/mol

(d) 98.01 g/mol

Question: The acqueous solution of NACl on electrolysis gives

The Electrolysis of Aqueous NaCl

The figure below shows an idealized drawing of a cell in which an aqueous solution of sodium chloride is electrolyzed.

Once again, the Na+ ions migrate toward the negative electrode and the Cl- ions migrate toward the positive electrode. But, now there are two substances that can be reduced at the cathode: Na+ ions and water molecules.

Cathode (-):

Na+ + e- Na

Eored = -2.71 V

2 H2O + 2 e- H2 + 2 OH-

Eored = -0.83 V

Because it is much easier to reduce water than Na+ ions, the only product formed at the cathode is hydrogen gas.

Cathode (-):

2 H2O(l) + 2 e- H2(g) + 2 OH-(aq)

There are also two substances that can be oxidized at the anode: Cl- ions and water molecules.

Anode (+):

2 Cl- Cl2 + 2 e-

Eoox = -1.36 V

2 H2O O2 + 4 H+ + 4 e-

Eoox = -1.23 V

The standard-state potentials for these half-reactions are so close to each other that we might expect to see a mixture of Cl2 and O2 gas collect at the anode. In practice, the only product of this reaction is Cl2.

Anode (+):

2 Cl- Cl2 + 2 e-

At first glance, it would seem easier to oxidize water (Eoox = -1.23 volts) than Cl- ions (Eoox = -1.36 volts). It is worth noting, however, that the cell is never allowed to reach standard-state conditions. The solution is typically 25% NaCl by mass, which significantly decreases the potential required to oxidize the Cl- ion. The pH of the cell is also kept very high, which decreases the oxidation potential for water. The deciding factor is a phenomenon known as overvoltage, which is the extra voltage that must be applied to a reaction to get it to occur at the rate at which it would occur in an ideal system.

Under ideal conditions, a potential of 1.23 volts is large enough to oxidize water to O2 gas. Under real conditions, however, it can take a much larger voltage to initiate this reaction. (The overvoltage for the oxidation of water can be as large as 1 volt.) By carefully choosing the electrode to maximize the overvoltage for the oxidation of water and then carefully controlling the potential at which the cell operates, we can ensure that only chlorine is produced in this reaction.

In summary, electrolysis of aqueous solutions of sodium chloride doesn't give the same products as electrolysis of molten sodium chloride. Electrolysis of molten NaCl decomposes this compound into its elements.

electrolysis

2 NaCl(l)

2 Na(l) + Cl2(g)

Electrolysis of aqueous NaCl solutions gives a mixture of hydrogen and chlorine gas and an aqueous sodium hydroxide solution.

electrolysis

2 NaCl(aq) + 2 H2O(l)

2 Na+(aq) + 2 OH-(aq) + H2(g) + Cl2(g)

Because the demand for chlorine is much larger than the demand for sodium, electrolysis of aqueous sodium chloride is a more important process commercially. Electrolysis of an aqueous NaCl solution has two other advantages. It produces H2 gas at the cathode, which can be collected and sold. It also produces NaOH, which can be drained from the bottom of the electrolytic cell and sold.

The dotted vertical line in the above figure represents a diaphragm that prevents the Cl2 produced at the anode in this cell from coming into contact with the NaOH that accumulates at the cathode. When this diaphragm is removed from the cell, the products of the electrolysis of aqueous sodium chloride react to form sodium hypo-chlorite, which is the first step in the preparation of hypochlorite bleaches, such as Chlorox.

Cl2(g) + 2 OH-(aq) Cl-(aq) + OCl-(aq) + H2O(l)

The Electrolysis of Molten NaCl

An idealized cell for the electrolysis of sodium chloride is shown in the figure below. A source of direct current is connected to a pair of inert electrodes immersed in molten sodium chloride. Because the salt has been heated until it melts, the Na+ ions flow toward the negative electrode and the Cl- ions flow toward the positive electrode.

When Na+ ions collide with the negative electrode, the battery carries a large enough potential to force these ions to pick up electrons to form sodium metal.

Negative electrode (cathode):

Na+ + e- Na

Cl- ions that collide with the positive electrode are oxidized to Cl2 gas, which bubbles off at this electrode.

Positive electrode (anode):

2 Cl- Cl2 + 2 e-

The net effect of passing an electric current through the molten salt in this cell is to decompose sodium chloride into its elements, sodium metal and chlorine gas.

Electrolysis of NaCl:

Cathode (-):

Na+ + e- Na

Anode (+):

2 Cl- Cl2 + 2 e-

The potential required to oxidize Cl- ions to Cl2 is -1.36 volts and the potential needed to reduce Na+ ions to sodium metal is -2.71 volts. The battery used to drive this reaction must therefore have a potential of at least 4.07 volts.

This example explains why the process is called electrolysis. The suffix -lysis comes from the Greek stem meaning to loosen or split up. Electrolysis literally uses an electric current to split a compound into its elements.

electrolysis

2 NaCl(l)

2 Na(l) + Cl2(g)

This example also illustrates the difference between voltaic cells and electrolytic cells. Voltaic cells use the energy given off in a spontaneous reaction to do electrical work. Electrolytic cells use electrical work as source of energy to drive the reaction in the opposite direction.

The dotted vertical line in the center of the above figure represents a diaphragm that keeps the Cl2 gas produced at the anode from coming into contact with the sodium metal generated at the cathode. The function of this diaphragm can be understood by turning to a more realistic drawing of the commercial Downs cell used to electrolyze sodium chloride shown in the figure below.

Chlorine gas that forms on the graphite anode inserted into the bottom of this cell bubbles through the molten sodium chloride into a funnel at the top of the cell. Sodium metal that forms at the cathode floats up through the molten sodium chloride into a sodium-collecting ring, from which it is periodically drained. The diaphragm that separates the two electrodes is a screen of iron gauze, which prevents the explosive reaction that would occur if the products of the electrolysis reaction came in contact.

The feed-stock for the Downs cell is a 3:2 mixture by mass of CaCl2 and NaCl. This mixture is used because it has a melting point of 580oC, whereas pure sodium chloride has to be heated to more than 800oC before it melts.

Electrolysis of Water

A standard apparatus for the electrolysis of water is shown in the figure below.

electrolysis

2 H2O(l)

2 H2(g) + O2(g)

A pair of inert electrodes are sealed in opposite ends of a container designed to collect the H2 and O2 gas given off in this reaction. The electrodes are then connected to a battery or another source of electric current.

By itself, water is a very poor conductor of electricity. We therefore add an electrolyte to water to provide ions that can flow through the solution, thereby completing the electric circuit. The electrolyte must be soluble in water. It should also be relatively inexpensive. Most importantly, it must contain ions that are harder to oxidize or reduce than water.

2 H2O + 2 e- H2 + 2 OH-

Eored = -0.83 V

2 H2O O2 + 4 H+ + 4 e-

Eoox = -1.23 V

The following cations are harder to reduce than water: Li+, Rb+, K+, Cs+, Ba2+, Sr2+, Ca2+, Na+, and Mg2+. Two of these cations are more likely candidates than the others because they form inexpensive, soluble salts: Na+ and K+.

The SO42- ion might be the best anion to use because it is the most difficult anion to oxidize. The potential for oxidation of this ion to the peroxydisulfate ion is -2.05 volts.

2 SO42- S2O82- + 2 e-

Eoox = -2.05 V

When an aqueous solution of either Na2SO4 or K2SO4 is electrolyzed in the apparatus shown in the above figure, H2 gas collects at one electrode and O2 gas collects at the other.

What would happen if we added an indicator such as bromothymol blue to this apparatus? Bromothymol blue turns yellow in acidic solutions (pH < 6) and blue in basic solutions (pH > 7.6). According to the equations for the two half-reactions, the indicator should turn yellow at the anode and blue at the cathode.

Cathode (-):

2 H2O + 2 e- H2 + 2 OH-

Anode (+):

2 H2O O2 + 4 H+ + 4 e-

Faraday's Law

Faraday's law of electrolysis can be stated as follows. The amount of a substance consumed or produced at one of the electrodes in an electrolytic cell is directly proportional to the amount of electricity that passes through the cell.

In order to use Faraday's law we need to recognize the relationship between current, time, and t