CHEMICAL REACTIONS

CHEMICAL REACTIONSCH. 11

What is a cation afraid of? A dogion!

Prior Knowledge Activity

• C6H12O6 + O2 → CO2 + H2O

• Write down everything you know about it including compounds involved and how many atoms of each element are in each molecule, names, etc... Balance the equation.

Describing a Chemical Reaction

Indications of a Chemical Reaction

– Evolution of heat, light, and/or sound

– Production of a gas

– Formation of a precipitate

– Color change

Signs of Chemical Reactions

There are five main signs that indicate a chemical reaction has taken place:

change in color change in odor production of newgases or vapor

input or releaseof energy

difficult to reverse

rele

ase

inpu

t

Word Equations

• Reactants Products• Iron + oxygen iron(III) oxide• (yields, forms, produces, etc…)

• *Burning a substance typically requires oxygen, so methane and oxygen are the reactants. The products are water and carbon dioxide. Write the word equation:

• *

Chemical Equations

• Chemical equation = a representation of a chemical reaction• Skeleton equation = a chemical equation that does not

indicate the relative amounts of the reactants and products• States of substances – (s) = solid, (l) = liquid, (g) = gas, (aq) =

substance in aqueous solution (dissolved in water )– Fe(s) + O2(g) → Fe2O3(s)

• Catalyst = a substance that speeds up the reaction but is not used up in the reaction– H2O2(aq) H2O(l) + O2(g) *Say the word equation

• Don’t forget diatomic molecules (HOBrFINCl twins or the BrINClHOF brothers)

MnO2

• *C.P. 11.1 pg. 324• *P.P. 1-2 pg. 324

Balancing Chemical Equations

• Balanced equation = each side of the equation has the same number of atoms of each element and mass is conserved

• Coefficients = small whole numbers that are placed in front of the formulas in an equation in order to balance it– 1. write the skeleton equation– 2. use coefficients to balance the equation so it

obeys the law of conservation of mass

Cl

Cl

ClH

H

H

ClClCl

ClHH

H

H

H2 + Cl2 HCl H2 + Cl2 2 HCl

reactants products

H

Cl

reactants products

H

Cl

2

2

2 2

2 2

1

1

(unbalanced) (balanced)

Unbalanced and Balanced Equations

Hints and Steps to Balancing Chemical Equations

• 1. Start at the ugliest or muddiest formula first• 2. Leave the ‘lonely’ formulas to the end, you can always

put any number in front of those• 3. Treat polyatomic ions like one unit, don’t treat each atom

by itself• 4. It’s a game of Trial and Error• 5. Have to have same amount of atoms of each element on

the left as the right• 6. Even/odd – make them all even (sometimes doubling

everything will do the trick)• 7. Coefficients must be lowest whole number ratio

Practice• C.P. 11.2, P.P. 3-4 pg. 327• C.P. 11.3, P.P. 5-6 pg. 328• **CaSiO3 + HF → CaF2 + SiF4 + H2O

• HCl + HNO3 → HOCl + NO + H2O

• Li2O2 + CO2 → Li2CO3 + O2

• Ag2S + Al → Ag + Al2S3

• aluminum sulfate + calcium hydroxide → aluminum hydroxide + calcium sulfate

• Phosphoric acid + sodium hydroxide yields sodium phosphate and water• CuCl2 + Al → AlCl3 + Cu• Dicarbon dihydride reacts with oxygen to form carbon dioxide and water• 11.1 sect. assess. Pg. 329

Types of Chemical Reactions

• 6 Types of chemical reactions• Sometimes a reaction can fit into two categories• 1) Combination (synthesis)• 2) Decomposition• 3) Single-replacement• 4) Double-replacement• 5) Combustion• 6) Neutralization

A + B AB

AB A + B

A + BC AC + B

AB + CD AD + CB

HX + BOH BX + HOH

CH + O2 CO2 + H2O

Synthesis (combination)

• Combination = a chemical change in which two or more substances react to form a single new substance

• Metal and nonmetal– 2Mg(s) + O2(g) → 2MgO(s)

• Two nonmetals (more than 1 product possible)– S(s) + O2(g) → SO2(g)

– 2S(s) + 3O2(g) → 2SO3(g)

• Transition metal and nonmetal (more than 1)– Fe(s) + S(s) → FeS(s) – 2Fe(s) + 3S(s) → Fe2S3(s) – *C.P. 11.4, P.P. 13-14 pg. 331

A + B AB

Decomposition

• Decomposition reaction = a chemical change in which a single compound breaks down into two or more simpler products

• 1 reactant and two or more products– 2HgO(s) → 2Hg(l) + O2(g)

• Tips for decomposition:– 1. metal hydroxides always decompose to metal oxide and H2O– 2. Most binary compounds will break down into their elements

• Exception: PbO2 → PbO + O2

– 3. All carbonates (CO3) break down to the oxide and CO2

– 4. Chlorates (ClO3) break down to binary salt and O2

• C.P. 11.5, P.P. 15-16 pg. 332

AB A + B

Single-replacement• Single-replacement = a chemical change in which one element replaces a

second element in a compound• Both the reactants and products consist of an element and a compound

– 2K(s) + 2H2O(l) → 2KOH(aq) + H2(g)

– Zn(s) + Cu(NO3)2(aq) → Cu(s) + Zn(NO3)2(aq)

• Whether one metal will displace another metal from a compound depends upon the relative reactivities of the two metals

• As a rule (not always), transition metals have the same oxidation number in a reaction: EX: Fe+2 + Cu+2(OH)2 →

• Activity series = lists metals in order of decreasing reactivity – A reactive metal will replace any metal listed BELOW it in the activity series– Also works for halogens as well– Br2(aq) + NaI(aq) → NaBr(aq) + I2(aq)

– Br2(aq) + NaCl(aq) → No Reaction (NR)

• *C.P. 11.6, P.P. 17 pg. 334

A + BC AC + B

Mg + AlCl3

Al + MgCl2

Predict if these reactions will occur

Al + MgCl2

Can magnesium replace aluminum?

Activity Series

YES, magnesium is more reactive than aluminum.

2 23 3

Can aluminum replace magnesium?

Activity Series

NO, aluminum is less reactive than magnesium.

Therefore, no reaction will occur.

No reaction

MgCl2 + Al No reaction

The question we must ask is can the single element replace its counterpart? metal replaces metal or nonmetal replaces nonmetal.

Order of reactants DOES NOT

determine how they react.

LiRbKBaCaNaMgAlMnZnCrFeNiSnPbH2

CuHgAgPtAu

F2

Cl2Br2

I2

Halogen Reactivity

Element Reactivity

Double-Replacement

• Double-replacement reaction = a chemical change involving an exchange of positive ions between two compounds

• For this to occur, usually one of the following is produced: a molecular compound like water, a gas, or a slightly soluble precipitate– Ca(OH)2(aq) + 2HCl(aq) → CaCl2(aq) + 2H2O(l)

– 2NaCN(aq) + H2SO4(aq) → 2HCN(g) + Na2SO4(aq)

– Na2S(aq) + Cd(NO3)2(aq) → CdS(s) + 2NaNO3(aq)

• *C.P. 11.7, P.P. 18-19 pg. 335

AB + CD AD + CB

Combustion

• Combustion reaction = a chemical change in which an element or a compound reacts with oxygen, often producing energy in the form of heat and light

• Usually a hydrocarbon and oxygen react to produce carbon dioxide and water– 2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l)

– 2Mg(s) + O2(g) → 2MgO(s)

– S(s) + O2(g) → SO2(g)

• *C.P. 11.8, P.P. 20-21 pg. 337• *11.2 sect. assess. 22-27 pg. 339

CH + O2 CO2 + H2O

Neutralization

• Neutralization = a chemical reaction in which an acid and a base react to form a salt.

• Water is frequently produced as well.– HCl + NaOH → NaCl + H2O

HX + BOH BX + HOH

Net Ionic Equations

• Complete ionic equation = an equation that shows dissolved ionic compounds as dissociated free ions

• Net ionic equation = an equation for a reaction in solution that shows only those particles that are directly involved in the chemical change

Cont…

• Spectator ion = an ion that appears on both sides of an equation and is not directly involved in the reaction

• A net ionic equation shows only those particles involved in the reaction and is balanced with respect to both mass and charge

• *C.P. 11.9, P.P. 28 pg. 343

FeCO3

Na1+Fe2+

iron (II) chloride + sodium carbonate

Cl2

Using a SOLUBILITY TABLE:sodium chloride is soluble

iron (II) carbonate is insoluble

CO3

Fe2+

Fe

Na1+

Na2

Cl1- CO32- Cl1- CO3

2-

NaCl

sodium chloride iron (II) carbonate+

(aq) (ppt)

2FeCl2 Na2CO3 NaCl FeCO3(aq) (ppt)+ +

Predict if a reaction will occur when you combine aqueous solutions of iron (II) chloride with aqueous sodium carbonate solution.

If the reaction does occur, write a balanced chemical equation showing it.(be sure to include phase notation)

(aq) (aq)

Balanced chemical equation

Complete Ionic Equation

Fe2+(aq) + 2Cl1-(aq) + 2Na1+(aq) + CO32-(aq) 2Na1+(aq) + 2Cl1-(aq) + FeCO3(s)

Predicting the Formation of a Precipitate

• You can predict the formation of a precipitate by using the general rules for solubility of ionic compounds

• *11.3 Sect. Assess. Pg. 344

If you're not part of the solution, you're part of the precipitate.

TABLE OF SOLUBILITIES IN WATER

aluminum ss s n s n i s s i s d

ammonium s s s s s s s s s s s

barium s s i s i s s s i i d

calcium s s i s s ss s s i ss d

copper (II) s s i s i i n s i s i

iron (II) s s i s n i s s i s i

iron (III) s s n s i i n s i ss d

lead s ss i ss i i ss s i i i

magnesium s s i s s i s s i s d

mercury (I) ss i i i ss n i s i ss i

mercury (II) s ss i s ss i i s i d i

potassium s s s s s s s s s s s

silver ss i i i ss n i s i ss i

sodium s s s s s s s s s s s

zinc s s i s s i s s i s i

acet

ate

brom

ide

carb

onat

e

chlo

ride

chro

mat

e

hydr

oxid

e

iodi

de

nitr

ate

pho

sph

ate

sulfa

te

sulfi

de

i = insolubless = slightly solubles = solubled = decomposesn = not isolated

SOLIDSOLIDAQUEOUS

Legend

Bellringer 1

• Balance the following chemical equations• 1. (NH4)3PO4 + Pb(NO3)4 →Pb3(PO4)4 + NH4NO3

• 2. ammonia mixes with oxygen to form nitrogen monoxide and water

• 3. C2H6 + O2 →H2O + CO2 • 4. iron and sulfuric acid react to produce

iron(III) sulfate and hydrogen gas• 5. BF3 + Li2SO3→ B2(SO3)3 + LiF

Answers BR I

• 4 + 3 → 1 + 12• 4 + 5 → 4 + 6• 2 + 7 → 6 + 4• 2 + 3 → 1 + 3• 2 + 3 → 1 + 6

Bellringer 2

Answers BRII