Chapter 11Chapter 11

Chemical ReactionsChemical Reactions

Anything in black letters = write it in your notes (‘knowts’)

Chemical equations represent chemical reactions

Reactants Products

Reactant mass = Product mass

# reactant atoms = # product atoms

Chemical equations must be balanced to obey the LAW!

11.1 – Describing Chemical Rxns11.1 – Describing Chemical Rxns

Word Equations

“Sodium carbonate reacts with calcium chloride to produce sodium chloride and calcium carbonate”

Chemical Equations

Na2CO3 + CaCl2 NaCl + CaCO3

This is a ‘skeleton’ equation It is NOT balanced

Na2CO3 + CaCl2 NaCl + CaCO3

When balancing equations, never change subscripts.

Instead, add coefficients

2

subscripts coefficient

When balancing equations, never change subscripts. Instead, add coefficients

H2 + O2 → H2O22

Al + F2 → AlF32 23

NaClO3 → NaCl + O22 2 3

More on Chemical Equations

Symbols Used in Chemical Equations

Symbol Explanation

Use in place of → for reversible reactions

(s), (l), (g) Designates a reactant or product in the solid state, liquid state, or gaseous state; placed after the formula

(aq) Designates an aqueous solution; the substance is dissolved in water; placed after the formula

Indicates that heat is supplied to the reaction

A formula written above or below the yields sign indicates its use as a catalyst (in this example, platinum).

Δ

heat

Pt

or

Catalyst – substance that speeds up a chem. rxn but is not part of the chem. equation

ASSIGNMENT:

Chapter 11 #1-11 (p. 349 – 354)

Common acids:

H2SO4 – sulfuric acid

HCl – hydrochloric acid

HNO3 – nitric acid

Balancing Equations Help…

1. Balance 1 element at a time, from left to right.

2. Treat any polyatomic ions as single units if they are on both sides of the reaction.

Zn(OH) 2 + H3PO4 → Zn3(PO4)2 + H2O3 2 6

(OH) is NOT on both sides

There is a (PO4) on each side

Balancing Equations Hints…

3.Odd # atoms → even # atoms; multiply through by 2

4. Balance oxygen last, it just helps sometimes.

CH3OH + O2 → CO2 + H2O22 24

3

5. Remember, N2, O2, F2, Cl2, Br2, I2, H2

Ch. 6 Quiz #1

1. FeCl3 + H2S → FeCl2 + HCl + S

2. MnO2 + HCl → MnCl2 + H2O + Cl2

Balance the following chemical equations

Hydrochloric acid reacts with solid sodium hydrogen carbonate. The products formed are aqueous sodium

chloride, water, and carbon dioxide gas. Write a skeleton equation for this chemical reaction.

11.2 – Types of Chemical Rxns11.2 – Types of Chemical Rxns

Most chemical rxns will fit into 1 of 5 types.

1. Combination

2. Decomposition

3. Single Replacement

4. Double Replacement

5. Combustion

1. Combination

A + B → AB

Magnesium metal and oxygen gas combine to form the compound magnesium oxide.

2Mg(s) + O2 → 2 MgO(s)

2. Decomposition

AB → A + B

2HgO(s) 2Hg(l) + O2(g)heat

3. Single Replacement

A + BC → AB + C

2K(s) + 2H2O(l) → 2KOH(aq) + H2

4. Double Replacement

AB + CD → AC + BD

5. Combustion

A substance reacts with oxygen (O2) and releases energy

If the substance is a hydrocarbon, then CO2 and H2O are products,

CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)

Which type of reaction?

2K(s) + Cl2(g) → 2KCl(s)

S(s) + O2(g) → SO2(g)

2Fe(s) + 3S(g) → Fe2S3(s)

2NaN3(s) → 2Na(s) + 3N2(g)

H2O H2(g) + O2(g)electricity

K2CO3(aq) + BaCl2(aq) → 2KCl(aq) + BaCO3(s)

2KI(aq) + Pb(NO3)2(aq) → PbI2 + 2KNO3(aq)

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

Cl2(aq) + 2NaBr(aq) → 2NaCl(aq) + Br2(aq)

2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(g)

2Mg(s) + O2(g) → 2MgO(s)

Cu(s) + S(s) → CuS(s)

a) Al + F2 → AlF3

b) C3H8 + O2 → CO2 + H2O

c) FeSO4 + Ba(OH)2 → Fe(OH)2 + BaSO4

d) NaClO3 → NaCl + O2

Can you do these?

4Ag + O2 → Ag2O2

What does a coefficient mean?

_____ atoms of Ag will react with _____ molecule(s) of O2 to form _____ formula units of Ag2O

A coefficient represents the combining ratio of reactants & products in a chemical rxn.

Exploratory info for next chapters…

4 Ag + O2 → Ag2O21. How many molecules of oxygen (O2) would be needed to react with 4 atoms of silver?

2. How many molecules of oxygen (O2) would be needed to react with 8 atoms of silver?

3. How many formula units of silver oxide would be formed in 1? In 2?

Exploratory info for next chapters…

4 Ag + O2 → Ag2O2

How many oxygen molecules would be needed to form 20 formula units of silver oxide?

How many atoms of silver would be required as well?

Exploratory info for next chapters…

4 Ag + O2 → Ag2O2

If 20 atoms of silver react with 20 molecules of oxygen, which reactant would be used up completely? Which reactant would be leftover?

How many formula units of silver oxide would be formed?

Exploratory info for next chapters…

Limiting Reactant -

Reactant that is completely used up; limits the amount of product that can be produced.

Excess Reactant -

Reactant that remains un-reacted; is not completely used up.

Exploratory info for next chapters…

1. How many molecules of CO are needed to produce 4 atoms of Fe?

6 CO molecules

Fe2O3 + CO → Fe + CO23 2 3

2. How much Fe2O3 is assumed to be present in the question above?

Assuming that there is at least 2 formula units of Fe2O3

Exploratory info for next chapters…

ASSIGNMENT:

Chapter 11 Worksheet #2

38.

a)2Mg + O2 2MgO

b)4P + 5O2 2P2O5

c)Ca + S CaS

Chapter 11 #38,39,41-44,48-55 (p. 377)

39.

a)2Ag2O 4Ag + O2

b)NH4NO3 N2O + 2H2O

41.

a)H2C2O4 + 2KOH K2C2O4 + 2H2O

b)CdBr2 + Na2S CdS + 2NaBr

Chapter 11 #38,39,41-44,48-55 (p. 377)

42.

a)C4H8 + 6O2 4CO2 + 4H2O

b)C3H6O + 4O2 3CO2 + 3H2O

43.

a)3Hf + 2N2 Hf3N4; combination

b)Mg + H2SO4 MgSO4 + H2; sngl. rpl.

c)2C2H6 + 7O2 4CO2 + 6H2O; combustion

d)Pb(NO3)2 + 2NaI PBI2 + 2NaNO3; dbl. rpl.

Chapter 11 #38,39,41-44,48-55 (p. 377)

44.

Every decomposition rxn has a single reactant.

48.

a)Cl2 + 2KI I2 + 2KCl

b)2Fe + 6HCl 2FeCl3 + 3H2

c)P4O10 + 6H2O 4H3PO4

Chapter 11 #38,39,41-44,48-55 (p. 377)

49.

a)Cl2 + 2NaI 2NaCl + I2

b)2NH3 N2 + 3H2

c)4Na + O2 2Na2O

50.

a)ZnS + H2SO4 H2S + ZnSO4

b)NaOH + HNO3 H2O + NaNO3

c)2KF + Ca(NO3)2 CaF2 + 2KNO3

Chapter 11 #38,39,41-44,48-55 (p. 377)

51.

a)Na2O + H2O 2NaOH

b)H2 + Br2 2HBr

c)Cl2O7 + H2O 2HClO4

52.

a)Fe + H2SO4 FeSO4 + H2

b)No rxn

c)Br2 + BaI2 BaBr2 + I2

Chapter 11 #38,39,41-44,48-55 (p. 377)

53.

a)Tube a contains the sodium metal

b)2Na + 2H2O 2NaOH + H2; sngl. rpl.

54.

a)2C8H18 + 25O2 16CO2 + 18H2O

b)C6H12O6 + 6O2 6CO2 + 6H2O

c)HC2H3O2 + 2O2 2CO2 + 2H2O

Chapter 11 #38,39,41-44,48-55 (p. 377)

55.

a)2Al2O3 4Al + 3O2

b)Sn(OH)4 SnO2 + 2H2O

c)Ag2CO3 Ag2O + CO2