Unit 9 Chemical Reactions

UNIT 9 – CHEMICAL REACTIONS

Textbook: Chapter 4 Section 4.5 Oxidation-Reduction (REDOX) reactions

Section 4.6 Elements in Redox reactions

Differentiate between

§ Synthesis reactions

§ Hydrocarbon combustion reactions

§ Single replacement reactions

§ Decomposition reactions

§ Double replacement reactions (review)

Be able to:

o Predict the product of a chemical reaction

o Write half reactions for redox

o Balance redox equations

Problems:

Chapter 4: Skill building: 64, 65, 69, 70, 78

Elements in Redox: 87 (modify directions – classify as synthesis, decomposition, or single replacement)

88 (modify directions – classify as synthesis, decomposition, or single replacement)

91, 92, 93, 95 (a-d), 104

DEFINE THE FOLLOWING TERMS:

Oxidation

Reduction

Oxidizing agent

Reducing agent

ELECTROMOTIVE SERIES

Li / ® / Li+ / 2F- ® F2
Rb / ® / Rb+ / 2O2- ® O2
K / ® / K+ / 2Cl- ® Cl2
Cs / ® / Cs+ / 2Br- ® Br2
Ba / ® / Ba+2 / 2I- ® I2
Sr / ® / Sr+2
Ca / ® / Ca+2
Na / ® / Na+
Mg / ® / Mg+2
Ce / ® / Ce+3
Be / ® / Be+2
U / ® / U+3
Al / ® / Al+3
V / ® / V+2
Mn / ® / Mn+2
Si / ® / Si+4
Zn / ® / Zn+2
Cr / ® / Cr+3
Ga / ® / Ga+3
S-2 / ® / S
Fe / ® / Fe+2
Cd / ® / Cd+2
Tl / ® / Tl+2
Co / ® / Co+2
Ni / ® / Ni+2
Sn / ® / Sn+2
Pb / ® / Pb+2
H2 / ® / 2H+
Cu / ® / Cu+2
Ag / ® / Ag+1
Hg / ® / Hg+2
Au / ® / Au+1

COMBUSTION REACTIONS – Complete and balance Translate all words into symbols first.

1) C6H6 + O2 ®

2) C6H6 + O2

3) C5H12 + O2 ®

4) C2H4 + O2

5) C2H4 + O2 ®

6) C3H8 + O2 ®

7) C8H18 + O2

8) C27H45OH + O2 ®

9) C18H36O2 + O2 ®

10) C8H8 + O2 ®

11) C22H44 + O2

12) CH3OH + O2 ®

13) C6H12O6 + O2 ®

14) C2H5OH + O2 ®

15) C4H9OH + O2 ®

SYNTHESIS OR COMBINATION REACTIONS – Complete and balance Translate all words into symbols.

1. Al + O2 ®

2. K + F2 ®

4. Na + Cl2 ®

5. barium + chlorine ®

6. iron (II) + oxygen ®

7. magnesium + sulfur ®

8. sodium + oxygen ®

9. silver + iodine ®

10. aluminum + chlorine →

11. potassium + nitrogen ®

15. copper (II) + oxygen ®

16. tin (II) + bromine ®

17. sodium + sulfur ®

18. aluminum + oxygen ®

19. calcium + chlorine ®

20. magnesium + phosphorus ®

SINGLE REPLACEMENT Complete and balance the following reactions. Be sure to use the electromotive series. Translate all words into symbols first.

1) Barium nitrate + potassium

2) Cobalt (II) chloride + gallium

3) Sodium sulfite + aluminum

4) Copper (II) sulfate + chromium

5) Zn + KOH ®

6) Fe + H2O ®

7) F2 + AlCl3 ®

8) Au + AgNO3 ®

9) Potassium + water

10) Chlorine + copper (I) iodide

11) Bromine + potassium fluoride

12) Bromine + potassium iodide

13) Magnesium + water

14) Fe + SnBr2 ®

15) Zn + Fe(HSO4)3 ®

16) Na + Al2(SO4)3 ®

17) Cu + AgNO3 ®

18) Zn + HCl ®

19) Magnesium bromide + chlorine

20) Potassium + sodium chloride

21) Water + aluminum

22) Ba + Na3PO4 ®

23) Sr3(PO4)2 + Li ®

24) CdCl2 + Mg ®

25) Ca + Pb(SO4)2 ®

DECOMPOSITION – Complete and balance

KClO3

Ba(HCO3)2

Ag2O

Pb2O

Al2O3

NaOH

Pb(ClO4)4

H2SO4

NaClO

Al(OH)3

CdCO3

Mg(OH)2

BaCl2

NaHCO3

H2CO3

Lithium carbonate heated ®

Calcium chlorate heated ®

Zinc hydrogen carbonate heated ®

Silver oxide heated ®

Sodium chloride electrolysis ®

Potassium hydroxide heated ®

Iron (III) hydroxide heated ®

Carbon disulfide electrolysis ®

Barium carbonate heated ®

Aluminum hydrogen carbonate heated ®

Phosphoric acid heated ®

Nitric acid heated ®

Water electrolysis ®

Sulfurous acid heated ®

OXIDATION NUMBERS:

Rules:

1. The atoms in a pure element (Fe, Zn, Br, O2, Mg, etc.) have an oxidation number of zero

2. The more electronegative element is assigned an oxidation number with the negative charge it would normally carry if it was an ion. The less electronegative element is assigned an oxidation number with a positive charge that it would normally have if it was an ion.

3. Fluorine always has an oxidation number of –1 in all compounds. (Most electronegative atom)

4. Oxygen has an oxidation # of –2 in almost all of its compounds. Exceptions: Peroxides such as H2O2 – oxidation number = -1 and when oxygen combines with a halogen such as fluorine. (OF2 – oxidation # = +2)

5. Hydrogen has an oxidation # of +1 in ALL compounds containing elements that are more electronegative than Hydrogen. It has an oxidation number of –1 when combined with metals.

6. The sum of all the oxidation numbers of a neutral compound MUST BE ZERO!

7. The sum of the oxidation numbers in a polyatomic ion MUST BE EQUAL TO THE CHARGE ON THE ION.

Determine the oxidation numbers of all the atoms of the following elements:

1. HCl / 8. CF4
2. PCl3 / 9. SO2
3. HNO3 / 10. KH
4. P4O10 / 11. N2O5
5. GeCl2 / 12. HClO3
6. H2SO4 / 13. H3PO4
7. H2CO3 / 14. HNO3

OXIDATION-REDUCTION REACTIONS (REDOX REACTIONS)

In oxidation-reduction reactions, electrons are exchanged and the oxidation states of some of the reactants are changed during the reaction.

When an atom GAINS electrons, its oxidation number decreases – it is REDUCED

When an atom LOSES electrons, its oxidation number increases – it is OXIDIZED

There cannot be an oxidation without a reduction taking place as well.

OIL RIG

OIL – oxidation is loss

RIG – reduction is gain

▪ If an atom loses electrons, it must be giving these electrons to another atom. The atom that is losing the electrons is OXIDIZED. Because it gives electrons to another atom it is the REDUCING AGENT.

▪ If an atom gains electrons, it must be getting these electrons from another atom. The atom that is gaining the electrons is REDUCED. Because it takes the electrons from another atom it is called the OXIDIZING AGENT.

▪ HALF REACTIONS:

o There must be TWO half reactions in any redox reactions

Fe + 2HCl ® FeCl2 + H2

Fe ® Fe2+ + 2 e- oxidation

2H1+ + 2 e- ® H2 reduction

OXIDATION AND REDUCTION HALF REACTIONS

Each of the following atom/ion pairs undergoes the oxidation number change indicated below. For each pair, determine whether an oxidation or reduction has taken place, then write the electronic equation indicating the number of electrons lost or gained.

Reaction / Oxidation or reduction
1) K ® K1+
2) S ® S2-
3) Mg ® Mg2+
4) F1- ® F2
5) H2 ® H1+
6) O2- ® O2
7) Fe3+ ® Fe2+
8) Mn2+ ® MnO41-

In each of the following equations, indicate the element that has been oxidized and the element that has been reduced. Label the oxidation state of each element. Write the half reaction for the oxidation reaction and the reduction reaction. Balance the equation. Indicate the type of reaction (synthesis, combustion, decomposition, single replacement)

1) Na + FeCl2 ® NaCl + Fe
2) C2H2 + O2 ® CO2 + H2O
3) PbS + O2 ® SO2 + PbO
4) H2 + O2 ® H2O
5) KClO3 ® KCl + O2
6) AgNO3 + Cu ® CuNO3 + Ag
7) Na + H2O ® NaOH + H2
8) Mg + ZnCl2 ® Zn + MgCl2
9) H2 + OF2 ® H2O + HF
10) CH4 + O2 ® CO2 + H2O

For each reaction below, indicate the oxidation numbers, write each half reaction and label each as oxidation or reduction, then balance the equation by balancing the half reactions and by inspection.

1) Mg + HCl ® MgCl2 + H2
2) Fe + V2O3 ® Fe2O3 + VO
3) KMnO4 + KNO2 + H2SO4 ® MnSO4 + H2O + KNO3 + K2SO4
4) K2Cr2O7 + SnCl2 + HCl ® CrCl3 + SnCl4 + KCl + H2O
5) HNO3 + P ® H3PO4 + NO2 + H2O
6) HNO3 + S ® NO2 + H2SO4 + H2O
7) CrCl3 + MnO2 + H2O ® MnCl2 + H2CrO4
8) HNO3 + Au + HCl ® H2O + NO + AuCl3
9) K2Cr2O7 + HCl + H2S ® KCl + CrCl3 + S + H2O
10) NaBr + MnO2 + H2SO4 ® NaHSO4 + MnSO4 + H2O + Br2

REVIEW – all reactions mixed (complete and balance)Indicate type of reaction (synthesis (S), single replacement (SR), double replacement (DR), decomposition (D), combustion (C))

1) Fe (III) + S ®

2) H2SO4 + BaCl2 ®

3) Al(HCO3)3

4) C4H8 + O2 ®

5) Na2CO3 + HCl ®

6) Mg + N2 ®

7) Zn + CuSO4 ®

8) NH4OH + H3PO4 ®

9) Cu + AgNO3 ®

10) Li + Br2 ®

11) CH4 + O2 ®

12) sodium mixed with water ®

13) Bi2(CO3)3

14) Na3PO4 + Fe(NO3)3 ®

15) LiOH

16) Al + Br2 ®

17) C6H6 + O2 ®

18) Cr(ClO4)3

19) Fe2O3 + I2 ®

20) Ca(OH)2

21) C2H5OH + O2 ®

22) 22) Copper (I) bromide + le

23) 23) Zinc + silver iodide

24) As(NO3)3 + H2S ®

25) C8H18 + O2

26) Tin (IV) acetate + zinc

27) Barium and chlorine

28) silver and copper(II) nitrate