Reactions & Equations Chemical reaction – process by which atoms of one or more

substances are rearranged to form a different substance Evidence/indicators of chemical reaction

Change in temperature (release or absorb heat) Light Color change Odor Gas/bubbles Precipitate (appearance of solid)

Reactants (what you start with) product (what you end up with)

Reactions & Equations continued Symbols used in equations

“reacts to produce”, “yields” - separates products and reactants

+ “added to”, “and”, “plus” – separates reactants or products

(s) solid(l) liquid(g) gas(aq) aqueous or water solution(ppt)solid was formed (precipitate) Heat was addedPt Catalyst was used

Reactions & Equations continued Write the word equation and skeleton equation for the

following statement: Solid iron and chlorine gas react to produce iron (III) chloride solid.

Word equation – use element/compound name iron(s) + chlorine (g) iron (III)chloride (s)

Skeleton equation – uses chemical formulas Fe(s) + Cl2(g) FeCl3(s)

Practice writing skeletal equations: hydrogen(g) + bromine(g) hydrogen bromide(g) carbon monoxide(g) + oxygen(g) carbon dioxide(g) potassium chlorate(s) potassium chloride (s) +

oxygen(g)

Reactions & Equations continued Balanced chemical equation

Observes law of conservation of mass Mass of products = mass of reactants Matter is not created or destroyed

Balance an equation by changing the coefficients ONLY Steps:

1. Write skeleton equation2. Count atoms in reactants3. Count atoms in products4. Change coefficients to make # of atoms of each element =

on each side5. Write coefficients in lowest ratio6. Check work

Reactions & Equations continued Practice Problem Write the balanced chemical equation in which aqueous sodium

hydroxide and aqueous calcium bromide react to produce solid calcium hydroxide and aqueous sodium bromide.

Classifying chemical reactions Synthesis reaction: A + B AB

2 or more reactants combine to form 1 product CaO(s) + H2O(l) Ca(OH)2(s)

Combustion reaction Oxygen combines with a substance and releases energy in

the form of heat and light C(s) + O2(g) CO2(g) 2H2(g) + O2(g) 2H2O(g) CH4(g) + 2O2(g) CO2(g) + 2H2O(g)

Decomposition: AB A + B Single compound breaks down into 2 or more elements or

new compounds. May require energy source. NH4NO3(s) N2O(g) + 2H2O(g)

Single Replacement

Reactions that involve an element replacing one part of a compound. The products include the displace element and a new compound. An element can only replace another element that is less active than itself. (Look a activity series)A +BX B+AX

Single Replacement Rules

1. Active metals replace less active metals from the less active metals’ compounds in aqueous solutionsex. 3Mg+ 2FeCl3—> 2Fe + 3MgCl2

2. Active metals replace hydrogen in waterex. 2Na + 2H2O—> H2 + 2NaOH

3. Active metals replace hydrogen in acids ex. 2Li + 2HCl —> H2 + 2LiCl

Single Replacement Rules, contd.

4. Active nonmetals replace less active nonmetals from their compounds in aqueous solutionsex. Cl2 + 2KI —> I2 + 2KCl

5. If a less reactive element is combined with a more reactive element in compound form, there will be no reactionex. Cl2 + KF —> no reaction*

Activity Series (Single Replacement)

Metals Li, Ca, Na, Mg, Al, Zn, Fe, Pb, [H2], Cu, Ag, Pt

NonmetalsF2, Cl2, Br2, I2,

More active More active Less Active Less Active

Classifying chemical reactions continued Use metal reactivity series to

determine if reaction can happen. Metals can only replace those below them on list.

Ag(s) + Cu(NO3)2(aq) NR Fe(s) + CuSO4(aq) Br2(g) + MgCl2(aq) Mg(s) + AlCl3(aq)

MetalsNonmetals

lithium fluorinerubidium oxygenpotassium chlorinecalcium brominesodium iodinemagnesiumaluminummanganesezincironnickeltinleadcoppersilverplatinumgold

Chart pg 288

Classifying chemical reactions continued Double Replacement Reactions: AB + CD AD + CB

Exchange of ions between 2 ionic compounds. All double replacement reactions produce either a solid, called a precipitate, gas, or water.

Solubility rules can be used to predict whether a reaction will occur

Make sure to pair up cation with an anion Al(NO3)3(aq) + H2SO4(aq)

Equations can be in more than 1 category.

Salt Solubility Rules1. All are soluble

o NO31-, ClO3

1-, C2H3O2 1-

2. All are solubleo alkali metals and NH4

+

3. All are soluble except compounds made with lead (II), silver, mercury (I), and HgCl2

o Cl1-, Br1-, I1-

4. All SO42- are soluble except PbSO4, Hg2SO4, BaSO4, CaSO4, Ag2SO4 are slightly

soluble5. All are insoluble except those made with Na+, K+, NH4

+, H+

o CO32-, PO4

3-, BO33-, SO3

2-, CrO42-, AsO4

3-

6. S2- are all insoluble except for Ba, Ca, Mg, Na, K, NH4, H

7. OH1- are insoluble except for Na, K, and NH41+ Ca(OH)2 and Ba(OH)2 are

moderately soluble.

Reactions in aqueous solutions Aqueous solutions – solvent is water

Solute – what is dissolved (sugar, kool-aid) Solvent – what dissolves (water, gasoline)

Ionic compounds separate n water NaOH Na+(aq) + OH-(aq)

Water doesn’t react in reaction; double replacement produce ppt, gas, or water

Complete ionic equation – ionic equation that shows all particles in solution as they exist 2NaOH (aq) + CuCl2(aq) 2NaCl(aq) + Cu(OH)2(s) 2 Na+(aq) + 2 OH-(aq) + Cu2+(aq) + 2Cl-(aq)

2Na+(aq) + 2Cl-(aq) + Cu(OH)2(s) Spectator ions do not participate in reaction

Reactions in aqueous solutions continued Net ionic equation – includes only particles that participate in

reaction (cross out spectator ions) 2 Na+(aq) + 2 OH-(aq) + Cu2+(aq) + 2Cl-(aq)

2Na+(aq) + 2Cl-(aq) + Cu(OH)2(s) 2 OH-(aq) + Cu2+(aq) Cu(OH)2(s)

Reactions that form water – no evidence of chemical reaction (water is colorless and odorless) HBr (aq) + NaOH(aq) H2O(l) + NaBr(aq) H+(aq) + Br-(aq) + Na+(aq) + OH-(aq)

H2O(l) + Na+(aq) + Br-(aq) H+(aq) + OH-(aq) H2O(l)

Reactions in aqueous solutions continued Reactions that form gases – see bubbles

2 HI(aq) + Li2S(aq) H2S(g) + 2LiI(aq) 2 H+(aq) + 2 I-(aq) + 2Li+(aq) + S2-(aq)

H2S(g) + 2 I-(aq) + 2Li+(aq) 2 H+(aq) + S2-(aq) H2S(g)

Net Ionic equations Bottom line – find the (s), (l), or (g) and write the ions that

create it. Write a balanced chemical equation, complete ionic equation

and a net ionic equation for the following reaction: Aqueous solutions of sodium carbonate and manganese

(V) chloride are mixed, forming the precipitate manganese (V) carbonate

Oxidation/Reduction Single replacement and combustion reaction involve transfer

of electrons (oxidation-reduction or redox reaction) Many synthesis and decomposition reactions also involve a

transfer of electrons Complete chemical equation: 2 Na(s) + Cl2(g) 2 NaCl(s) Net ionic equation: 2 Na(s) + Cl2(g) 2 Na+ + 2 Cl-

Electrons from 2 Na transferred to Cl2 molecule to form 2 Cl- ions

Oxidation/Reduction continued Write and balance the equation for the complete combustion

of the burning of magnesium

Write a net ionic equation

What gives up electron? What gains electron?

Oxidation/Reduction continued Oxidation is the loss of electrons Reduction is the gain of electrons LEO the lion says GER

Loss of electrons is oxidation and gain of electrons is reduction

OIL RIG Oxidation Involves Loss; Reduction Involves Gain

Oxidation/Reduction continued Write the complete chemical equation for the reaction

between potassium bromide solution and chlorine gas.

What loses electron(s)? What is this called? What gains electron(s)? What is this called?

Oxidation/Reduction continued Can look at oxidation # to determine the oxidizing agent or

reducing agent Oxidizing agent accepts electron (so it is reduced) Reducing agent loses electron (so it is oxidized)

loses e-2 K(s) + Br2(g) 2 KBr(s)

Oxidation # 0 0 1+ 1-gains e-

K loses e- (is oxidized) so is reducing agent Br gains e- (is reduced) so is oxidizing agent

Oxidation/Reduction continued Write balanced chemical equation for the production of

ammonia

Write in oxidation # of each element under equation What is oxidized? What is reduced? What is the oxidizing agent? What is the reducing agent?

Title: Ppt. Lab Purpose: To observe ppt reactions & practice writing

equations. Materials: CoCl2, NiCl2, FeCl3, CuCl2, NaOH Procedure:

1. In 4 well plates put 20 drops NaOH. 2. To each well, add 5 drops of one of the metal solutions.

Observations:

Conclusions: 1. Write a balanced equation for each reaction. 2. Write the net ionic equation for each reaction.

FeCl3 NiCl2 CoCl2 CuCl2

NaOH