chemistry chapter 8 chemical equations balancing formula equations
TRANSCRIPT
Chemistry Chapter 8 Chemical Equations
Balancing Formula Equations
What is a Chemical Reaction?
• A chemical reaction occurs when two or more substances are changed into different substances.
What is a Chemical Equation?
A chemical equation represents, with symbols and formulas, the identities and relative molecular or molar amounts of the reactants and products in a chemical reaction.
Indications of a Chemical Reaction
1) Evolution of energy as heat and light.
2) Production of a gas.
3) Formation of a precipitate.
4) Color change.
Characteristics of Chemical Equations
1) The equation must represent known facts.2) The equation MUST contain the correct
formulas for the reactants and products.3) The Law of Conservation of Mass must be
satisfied. We can use coefficients to satisfy this law.
*coefficients- a small whole number that appears in front of a formula in a chemical equation
Word & Formula Equations
• word equation- an equation in which the reactants and products of a reaction are represented by words
• formula equation- represents the reactants and products of a chemical reaction by their symbols & formulas
• balanced formula equation- uses coefficients to allow conservation of mass
Examples of the Types of Equations
word equation-iron II phosphate reacts with aluminum nitrate to produce iron II nitrate and aluminum phosphate
formula equation-Fe3(PO4)2 + Al(NO3)3 Fe(NO3)2 + AlPO4
balanced formula equation-Fe3(PO4)2 + 2 Al(NO3)3 3 Fe(NO3)2 + 2 AlPO4
Symbols Used in Chemical Equations
yields
(s) solid
(l) liquid
(aq) aqueous
(g) gas
Diatomic Elements
• There are seven common elements that are called the “diatomic elements”. Whenever they are pure elements and appear alone (NOT in a compound) in an equation, their symbol contains two atoms rather than one. They include:
hydrogen (H2) oxygen (O2) nitrogen (N2) fluorine (F2) chlorine (Cl2) bromine (Br2)
iodine (I2)
A simple mnemonic is “halogens HON”.
Practice Problemsms
• Do practice problems #1, #2, & #3 on page 268 of the textbook.
Practice Problem 1 page 268
1a) Ca (s) + S (s) CaS (s) already balanced
1b) H2 (g) + F2 (g) HF (g)
H2 (g) + F2 (g) 2 HF (g) balanced
1c) Al (S) + ZnCl2 (aq) Zn (s) + AlCl3 (aq)
2 Al(S) + 3 ZnCl2 (aq) 3 Zn(s) + 2 AlCl3(aq)
Practice Problem #2 page 268
2a) CS2(l) + O2(g) CO2(g) + SO2(g)
liquid carbon disulfide reacts with oxygen gas to produce carbon dioxide gas and sulfur dioxide gas
2b) NaCl(aq) + AgNO3(aq) NaNO3(aq) + AgCl(s)
aqueous sodium chloride reacts with aqueous silver nitrate to yield aqueous sodium nitrate and solid silver chloride
Practice problem #3 page 268
3) N2H4 + O2 N2 (g) + H2O
N2H4 + O2 N2 (g) + 2 H2O
Significance of a Chemical Equation
1) The coefficients of a chemical reaction indicate relative, not absolute, amounts of reactants and products.
2) The relative masses of the reactants and products of a chemical reaction can be determined from the reaction’s coefficients.
3) The reverse reaction for a chemical equation has the same relative amounts of substances as the forward reaction.
Rules for Balancing Chemical Equations
1) Identify the names of the reactants and products and write a word equation.
2) Write a formula equation by substituting correct formulas for the names of the reactants and products.
3) Using coefficients, balance the formula equation according to the law of conservation of mass.– Balance the different types of atoms one at a time.– First balance atoms of elements that appear only
once on each side.– Balance polyatomic ions that appear on both sides
as single units.– Balance H and O atoms after atoms of other
elements have been balanced.4) Count atoms to be sure the equation is balanced.
Balancing a Formula Equation
• hydrogen gas reacts with chlorine gas to produce hydrogen chloride gas
• _?_ H2(g) + _?_ Cl2(g) _?_ HCl(g)
• H2(g) + Cl2(g) 2 HCl(g)
Practice #1- Balance the following formula equations.Practice #1- Balance the following formula equations.
__CaF__CaF22 + __Na + __Na22S S __CaS + __ NaF __CaS + __ NaF
__FeS + __ AlPO__FeS + __ AlPO44 __Fe __Fe33(PO(PO44))22 + __Al + __Al22SS33
__Na + __Cl__Na + __Cl22 __NaCl __NaCl__H__H22 + __O + __O22 __H __H22OO
__C__C22HH44 + __O + __O22 __CO __CO22 + __H + __H22OO
__HBr + __NaOH __HBr + __NaOH __NaBr + __H __NaBr + __H22OO
__Na__Na22SOSO44 + __AlPO + __AlPO44 __Na __Na33POPO44 + __Al + __Al22(SO(SO44))33
__N__N22 + __O + __O22 __N __N33OO77
__FePO__FePO44 + __CaSO + __CaSO44 __Fe __Fe22(SO(SO44))33 + __Ca + __Ca33(PO(PO44))22
__CuBr__CuBr22 + __NaF + __NaF __CuF __CuF22 + __NaBr + __NaBr
Balanced Formula EquationBalanced Formula Equation
__CaF__CaF22 + __Na + __Na22S S __CaS + __ NaF __CaS + __ NaF
CaFCaF22 + Na + Na22S S CaS + 2 NaF CaS + 2 NaF 1:1:1:21:1:1:2
__FeS + __ AlPO__FeS + __ AlPO44 __Fe __Fe33(PO(PO44))22 + __Al + __Al22SS33
3 FeS + 2 AlPO3 FeS + 2 AlPO44 Fe Fe33(PO(PO44))22 + Al + Al22SS33 3:2:1:13:2:1:1
__Na + __Cl__Na + __Cl22 __NaCl __NaCl2 Na + Cl2 Na + Cl22 2 NaCl 2 NaCl 2:1:22:1:2
__H__H22 + __O + __O22 __H __H22OO
2 H2 H22 + O + O22 2 H 2 H22OO 2:1:22:1:2
__C__C22HH44 + __O + __O22 __CO __CO22 + __H + __H22OO
CC22HH44 + 3 O + 3 O22 2 CO 2 CO22 + 2 H + 2 H22OO 1:3:2:21:3:2:2
Practice
__HBr + __NaOH __HBr + __NaOH __NaBr + __H __NaBr + __H22OO
HBr + NaOH HBr + NaOH NaBr + H NaBr + H22OO 1:1:1:11:1:1:1
__Na__Na22SOSO44 + __AlPO + __AlPO44 __Na __Na33POPO44 + __Al + __Al22(SO(SO44))33
3 Na3 Na22SOSO44 + 2 AlPO + 2 AlPO44 2 Na 2 Na33POPO44 + Al + Al22(SO(SO44))33 3:2:2:13:2:2:1
__N__N22 + __O + __O22 __N __N33OO77
3 N3 N22 + 7 O + 7 O22 2 N 2 N33OO77 3:7:23:7:2
__FePO__FePO44 + __CaSO + __CaSO44 __Fe __Fe22(SO(SO44))33 + __Ca + __Ca33(PO(PO44))22
2 FePO2 FePO44 + 3 CaSO + 3 CaSO44 Fe Fe22(SO(SO44))33 + Ca + Ca33(PO(PO44))22 2:3:1:12:3:1:1
__CuBr__CuBr22 + __NaF + __NaF __CuF __CuF22 + __NaBr + __NaBr
CuBrCuBr22 + 2 NaF + 2 NaF CuF CuF22 + 2 NaBr + 2 NaBr 1:2:1:21:2:1:2
Practice Problems
• Do the following practice problems from the textbook:
practice #1 & #2 on page 272practice #1 (a, b, c) on page 274
section review #2, #3, #4, & #5 on page 274
Practice Problems page 2721a) Mg + HCl MgCl2 + H2
Mg + 2 HCl MgCl2 + H2
1b) HNO3 (aq) + Mg(OH)2 (s) Mg(NO3)2 (aq) + H2O (l)
2 HNO3 (aq) + Mg(OH)2 (s) Mg(NO3)2 (aq) + 2 H2O (l)
2) Ca(s) + H2O(l) Ca(OH)2 (aq) + H2 (g)
Ca(s) + 2 H2O(l) Ca(OH)2 (aq) + H2 (g)
Practice Problems page 274
1a) Na (s) + Cl2 (g) NaCl (s)
2 Na (s) + Cl2 (g) 2 NaCl (s)
1b) Cu (s) + AgNO3 (aq) Cu(NO3)2 (aq) + Ag (s)
Cu (s) + 2 AgNO3 (aq) Cu(NO3)2 (aq) + 2 Ag (s)
1c) Fe2O3 (s) + CO (g) Fe (s) + CO2 (g)
Fe2O3 (s) + 3 CO (g) 2 Fe (s) + 3 CO2 (g)
Section Review page 274
2) H2SO4 (aq) + NaOH (aq) Na2SO4 (aq) + H2O (l)
H2SO4 (aq) + 2 NaOH (aq) Na2SO4 (aq) + 2 H2O (l)
3a) solid potassium plus liquid water produce aqueous potassium hydroxide and hydrogen gas
3b) solid iron metal plus chlorine gas yields solid iron (III) chloride
4) H2S (g) + O2 (g) SO2 (g) + H2O (g)
2 H2S (g) + 3 O2 (g) 2 SO2 (g) + 2 H2O (g)
Section Review page 274
5) VO + Fe2O3 V2O5 + FeO
2 VO + 3 Fe2O3 V2O5 + 6 FeO
QUIZ #1- Balancing chemical equations
Balance the following formula equations.
1- ___C3H8 + ___O2 ___CO2 + ___H2O
2- ___Al2(SO4)3 + ___Fe3(PO4)2 ___AlPO4 + ___FeSO4
3- ___Na + ___Cl2 ___NaCl
4- ___N2 + ___O2 ___N3O7
5- ___NaNO3 + ___Al2(CO3)3 ___Na2CO3 + ___Al(NO3)3
Types of Chemical Reactions
synthesis reaction- also known as a composition reaction, two or more substances combine to form a new compound.
A + X AX
Could be called the ”Boy Meets Girl” reaction.
Types of Chemical Reactions
decomposition reaction- a single compound undergoes a reaction that produces two or more simpler substances.
AX A + X
The “Boy Loses Girl” reaction.
Types of Chemical Reactions
single-displacement reaction- also known as a replacement reaction, one element replaces a similar element in a compound.
A + BX AX + B
The “Boy Loses Girl to Best Friend” reaction.
Types of Chemical Reactions
double-displacement reaction- also known as a double replacement reaction, the ions of two compounds exchange places in an aqueous solution to form two new compounds.
AX + BY AY + BX
The “Best Friends Trade Girlfriends” Reaction.
Types of Chemical Reactions
combustion reaction- a substance combines with oxygen, releasing a large amount of energy in the form of light and heat
A + O2 AO + fire
The “Where There’s Smoke There’s Fire” reaction.
Reaction Types Summary
Synthesis A + X AX
Decomposition AX A + X
Single Displacement A + BX AX + B
Double Replacement AX + BY AY + BX
Combustion A + O2 AO + fire
QUIZ #2- Balance the following formula equations then identify the reaction type.
__Na + __Br2 __NaBr
reaction type=
__Fe2O3 __Fe + __O2
reaction type=
__CuI + __F2 __CuF + __I2
reaction type=
__FeSO4 + __Ca3(PO4)2 __Fe3(PO4)2 + __CaSO4
reaction type=
__C4H8 + __O2 __CO2 + __H2O (fire)
reaction type=
QUIZ #2- Balance the following formula equations then identify the reaction type.
__Na + __Br2 __NaBr 2 Na + Br2 2 NaBr synthesis (composition)
__Fe2O3 __Fe + __O2
2 Fe2O3 4 Fe + 3 O2decomposition
__CuI + __F2 __CuF + __I2
2 CuI + F2 2 CuF + I2single replacement (single displacement)
__FeSO4 + __Ca3(PO4)2 __Fe3(PO4)2 + __CaSO4
3 FeSO4 + Ca3(PO4)2 Fe3(PO4)2 + 3 CaSO4double replacement (double displacement)
__C4H8 + __O2 __CO2 + __H2O (fire)C4H8 + 6 O2 4 CO2 + 4 H2O (fire)combustion
Types of Chemical Reactions
synthesis reaction- also known as a composition reaction, two or more substances combine to form a new compound.
A + X AX
Journal Investigation- Synthesis Reaction
1) Get a strip of magnesium ribbon and an iron crucible from the front.
2) Roll the magnesium strip into a loose ball.3) Weigh & record the mass of the magnesium & crucible on
a scale. 4) Heat the crucible and magnesium using your burner until
the magnesium begins to glow. Turn off the burner.5) Allow the crucible to cool at least five minutes.6) Weigh and record the new mass of the crucible &
magnesium oxide product.7) Add three or four drops of tap water to the crucible. Waft
the gas produced to attempt to smell the odor of ammonia.
Safety Precautions
Burner & equipment become very hot. DO NOT touch. Handle with crucible tongs.
Eye protection MUST be worn due to possible sparks in the crucible.
Safety apron is to be worn to protect skin & clothing.
Use a wafting technique when trying to detect ammonia smell.
Rinse & dry the cool crucible after lab is finished.
Journal Investigation- Synthesis ReactionANALYSIS
1) Using the recorded masses, show how this proves a synthesis reaction occurred.
2) The magnesium (Mg) combined with oxygen (O2) in the air to form a magnesium oxide (MgO) product. Write a balanced formula equation for this reaction.
3) When you added water, you should have smelled ammonia (NH3). The formula equation for this reaction would be Mg3N2 + H2O Mg(OH)2 + NH3. Balance this formula equation.
4) Where did the nitrogen come from to form the Mg2N3 as another product of this synthesis reaction?
Types of Chemical Reactions
decomposition reaction- a single compound undergoes a reaction that produces two or more simpler substances.
AX A + X
Lab Investigation- Decomposition Reaction
1) Get a test tube with 5 – 10 mL of fresh hydrogen peroxide (H2O2) from the rack in the front of the room.
2) Add a match-head size amount of manganese dioxide (MnO2) to the test tube to act as a catalyst (a substance that speeds up a reaction without becoming part of it).
3) Observe the hydrogen peroxide for signs of a chemical reaction.
4) While the reaction is still taking place, set the end of a wooden splint on fire then blow it out.
5) While the splint is still glowing, lower it into the top of the test tube without touching the liquid. Observe the result. You can repeat this step several times until the reaction in the test tube stops.
Lab Investigation- Decomposition ReactionANALYSIS
1) Use your textbook to find the definition of a catalyst. Write the definition in the log.
2) What was the indication in the test tube that a chemical reaction was taking place?
3) Hydrogen peroxide decomposed into oxygen gas and liquid water. Write the balanced formula equation for this reaction.
4) What test was used to demonstrate that oxygen gas was a product of the reaction?
5) Write a balanced formula equation for the reaction between the carbon in the wood and the oxygen gas being produced. What type of chemical reaction is this?
Types of Chemical Reactions
single-displacement reaction- also known as a replacement reaction, one element replaces a similar element in a compound.
A + BX AX + B
Lab Investigation- Single Replacement Reaction
1) Get a small beaker with 20-25 mL. of silver nitrate (AgNO3). BE CAREFUL- silver nitrate will cause burn on your skin & clothing.
2) Record in your journal the color of the silver nitrate solution.3) Get a penny from your instructor.4) Gently lower the penny into the beaker of silver nitrate
making sure there is no splash.5) Record observation of the penny in your journal for 10
minutes at 1 minute intervals.6) Use a piece of tape to identify your beaker & penny. Place
the beaker in the fume hood overnight.7) Record your observations after 24 hours. Be sure to include
the color of the liquid in the beaker.
Lab Investigation- Single Replacement ReactionANALYSIS
1) What were the indications that a chemical reaction had taken place?
2) What were the products of the single replacement reaction between copper (Cu) and silver nitrate (AgNO3)? (Assume the product contains the copper I ion.)
3) Write the balanced formula equation for the reaction between copper and silver nitrate.
4) Based on your observations, which element, copper or silver would appear higher on an activity series of metals? Why?
Types of Chemical Reactions
double-displacement reaction- also known as a double replacement reaction, the ions of two compounds exchange places in an aqueous solution to form two new compounds.
AX + BY AY + BX
Lab Investigation- Double Replacement Reaction
1) Get a test tube with 5 mL. of silver nitrate (AgNO3). BE CAREFUL- silver nitrate will cause burns on your skin & clothing.
2) Record in your journal the color of the silver nitrate solution.
3) Get a test tube of sodium chloride (NaCl) solution. Record your observations of the solution.
4) Gently pour the sodium chloride into the test tube of silver nitrate making sure there is no splash.
5) Record your observation of the mixtures of the two aqueous solutions.
6) Take the test tubes to the front for disposal.
Lab Investigation- Double Replacement ReactionANALYSIS
1) What were the indications that a chemical reaction had taken place?
2) What were the products of the double replacement reaction between sodium chloride (NaCl) and silver nitrate (AgNO3)?
3) Which of these products is the precipitate?4) Write the balanced formula equation for the
reaction between aqueous sodium chloride and aqueous silver nitrate.
Types of Chemical Reactions
combustion reaction- a substance combines with oxygen, releasing a large amount of energy in the form of light and heat
A + O2 AO + fire
Just for Fun- The Kandy Killer
This will be a demonstration ONLY. 1) We will be heating potassium chlorate (KClO3).
This will cause it to undergo a decomposition reaction that produces potassium chloride and oxygen.
2) A glowing splint will be used to confirm that oxygen is being produced.
3) Candy will be dropped into the test tube. A rapid chemical reaction should be seen. YEA!!!
Practice Problems
section review problems: #1 through #5 on page 284 of the textbook.
Section Review page 284
1- List 5 types of reactions identified in this chapter.synthesisdecompositionsingle displacement (replacement)double displacement (replacement) combustion
2a- N2 + 3H2 2 NH3 synthesis
b- 2Li + 2H2O 2LiOH + H2 single displacement
c- 2NaNO3 2NaNO2 + O2 decomposition
d- 2C6H14 + 19O2 12CO2 + 14H2O combustion
3a-
QUIZ #3- Chemistry Chapter 8 Test Review
Balance the following equations & identify the reaction type.
1) __Ca(NO3)2 + __Na3PO4 __Ca3(PO4)2 + __NaNO3 reaction type:
2) __C4H8 + __O2 __CO2 + __H2O + fire reaction type:
3) __H2 + __Br2 __HBrreaction type:
4) __K + __HBr __KBr + __H2
reaction type:
5) __CaCO3 __CaO + __CO2
reaction type:
Activity Series of the Elements
• The activity of an element describes how it can react under specific conditions
• An activity series is a list of elements organized according to the ease with which elements undergo certain chemical reactions.
Activity Series of Metals
Most reactive:
LiRb React with cold water and acids,K replacing hydrogen.Ba React with oxygen forming oxidesSrCaNa
Activity Series of Metals2nd most reactive set:
MgAl React with steam (but not coldMn water) and acids, replacingZn hydrogen. React with oxygen,Cr forming oxides.FeCd
Activity Series of Metals
3rd most reactive set:
Co Do not react with water.Ni React with acids, replacing
hydrogen.Sn React with oxygen, forming oxides.Pb
Activity Series of Metals
4th most reactive set:
H2
Sb React with oxygen, forming oxides.BiCuHg
Activity Series of Metals
Least reactive set:
Ag Fairly unreactive, forming oxides only
Pt indirectly.Au
Activity of Halogen Non-metals
The following halogens will replace any other halogen below it in a single replacement reaction.
F2
Cl2
Br2
I2
Practice Problems
• Use table 3 on page 286 of the textbook to answer Practice Problems #1 through #3 on page 287.
Practice problems page 287
1a- ____ Cr + ____H2O (l) ?
cannot occur- Cr will not react with water, only steam
b- ____Pt + ____O2 ?
cannot occur-Pt does not form oxides directly
c- ____Cd + 2 HBr ? (HBr is an acid)can occur Cd reacts with acids to form hydrogenCd + 2 HBr CdBr2 + H2
d- ____Mg + ____H2O(g) ? H2O (g) is steam
can occur, Mg will react with steam to form hydrogenMg(s) + 2 H2O(g) Mg(OH)2 (aq) + H2 (g)
Practice Problems page 287
2- Identify the element that replaces hydrogen from acids but does not replace tin from its compounds.
Lead (Pb) replaces hydrogen from acids, but is below tin (Sn) in the activity series so it cannot replace tin (Sn).
3- According to table 3, what is the most active transition metal?
As you go down the activity series of metals, manganese (Mn) is the first transition metal in the list, so it is the most reactive transition metal.
QUIZ #4- Chemistry Chapter 8 Test Review
Use the activity series to determine if the following reactions are possible.
1) Sb + HCl (an acid)
2) K + ZnCl2
3) 2 HF + Cl2
4) 2 H2O (l) + 2 Na
5) MgBr2 + Cl2
Chemistry Chapter 8 Test
25 multiple choice questions: definition of a precipitate identify diatomic elements when used in chemical
equations rules for balancing equations identify a word equation symbols used in equations (eg. aq) determine coefficients needed to balance equations identify reaction types by definition & balanced formula
equations definitions of activity & activity series and how they are
used
Honors Chemistry Chapter 8 Test
35 multiple choice questions: chemical reactions & law of conservation of mass indicators of chemical reactionsdefinition of a precipitate and symbols used in equations identify a word equation & a formula equationdiatomic elements & how they are written in an equation Identify coefficients needed to balance formula equations rules for balancing formula equations reaction types by definition & balanced equations identifying & predicting products of reactionsdefinitions of activity & activity seriesuse activity series to predict products formed
Honors Chemistry Chapter 8 Test1 short answer question:
When balancing a formula equation, why must the formula subscripts remain unchanged?
1 essay question:Consider an equation. How does the equation violate the
law of conservation of mass? How can the equation be rewritten to conform to the law of conservation of mass?
3 problems:Write a balanced formula equation for a synthesis reaction
when given the reactants & product.Use an activity series to predict if a reaction can occur. If
yes, write the balanced formula equation. (2 of these)