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CHM 112
Section 1

Homework Assignment #28
Due April 21, 2006 by 8:05 a.m.

Practice (not to be turned in

): Practice reactions 51 - 70, 18.26, 18.27, 18.28, 18.29, 18.30, 18.31, 18.87

Complete and balance the reactions corresponding to the last digit

of your Student ID Number. This homework assignment will be worth 20 points.

0)

Cr(s) + HCl(aq) Cr3+(aq) + H2(g) + Cl(aq)

Mg(s) + O3(g) Mg(OH)2(s) + O2(g)

1)

HI(aq) + ClO3(aq) I3(aq) + Cl2(g)

Al(s) + ClO(aq) [Al(OH)4](aq) + Cl(aq)

2)

As2O3(s) + NO2(g) H3AsO4(aq) + NO(g)

Zn(s) + BrO(aq) [Zn(OH)4]2–(aq) + Br(aq)

3)

HBr(aq) + MnO2(s) Br2(l) + Mn2+(aq)

[Cr(OH)4](aq) + MnO4(aq) CrO42–(aq) + MnO2(s)

4)

H3AsO4(aq) + Al(s) AsH3(g) + Al3+(aq)

Co(OH)2(s) + ClO2(aq) Co(OH)3(s) + ClO(aq)

5)

HClO4(aq) + Fe2+(aq) ClO3(aq) + Fe3+(aq)

Ni(OH)3(s) + ClO2(aq) Ni(OH)2(s) + ClO3(aq)

6)

H2SO3(aq) + Ag(s) + Br(aq) AgBr(s) + S(s)

Co(OH)3(s) + NO2(aq) Co(OH)2(s) + NO3(aq)

7)

HNO3(aq) + Hg22+(aq) Hg2+(aq) + NO(g)

AgO(s) + Zn(s) Ag2O(s) + Zn(OH)2(s)

8)

NO2(g) + HCN(aq) C2N2(g) + HNO2(aq)

Ag2O(s) + Al(s) Ag(s) + Al(OH)3(s)

9)

H2S(aq) + BrO3(aq) BrO2(g) + S(s)

Mg(s) + ClO4(aq) Mg(OH)2(s) + ClO3(aq)



Answers:

0)

Cr(s) + HCl(aq) Cr3+(aq) + H2(g) + Cl(aq)

HCl(aq) indicates an acidic environment:

[ Cr(s) Cr3+(aq) + 3 e ] × 2 (oxidation)

[ 2 HCl(aq) + 2 e H2(g) + 2 Cl(aq) ] × 3 (reduction)

Net: 2 Cr(s) + 6 HCl(aq) 2 Cr3+(aq) + 3 H2(g) + 6 Cl(aq)

Mg(s) + O3(g) Mg(OH)2(s) + O2(g)

Mg(OH)2 indicates a basic environment:

Mg(s) + 2 H2O(l) Mg(OH)2(s) + 2 H+(aq) + 2 e (oxidation)

O3(g) + 2 H+(aq) + 2 e O2(g) + H2O(l) (reduction)

Net in acid: Mg(s) + O3(g) + H2O(l) Mg(OH)2(s) + O2(g)

Neutralization: none

Net: Mg(s) + O3(g) + H2O(l) Mg(OH)2(s) + O2(g)


1)

HI(aq) + ClO3(aq) I3(aq) + Cl2(g)

HI indicates an acidic environment:

[ 3 HI(aq) I3(aq) + 3 H+(aq) + 2 e ] × 5 (oxidation)

2 ClO3(aq) + 12 H+(aq) + 10 e Cl2(g) + 6 H2O(l) (reduction)

Net: 15 HI(aq) + 2 ClO3(aq) 5 I3(aq) + Cl2(g) + 3 H+(aq) + 6 H2O(l)

Al(s) + ClO(aq) [Al(OH)4](aq) + Cl(aq)

[Al(OH)4] indicates a basic environment:

[ Al(s) + 4 H2O(l) [Al(OH)4](aq) + 4 H+(aq) + 3 e ] × 2 (oxidation)

[ ClO(aq) + 2 H+(aq) + 2 e Cl(aq) + H2O(l) ] × 3 (reduction)

Net in acid: 2 Al(s) + 3 ClO(aq) + 5 H2O(l) 2 [Al(OH)4](aq) + 3 Cl(aq) + 2 H+(aq)

Neutralization: 2 H+(aq) + 2 OH(aq) 2 H2O(l)

Net: 2 Al(s) + 3 ClO(aq) + 2 OH(aq) + 3 H2O(l) 2 [Al(OH)4](aq) + 3 Cl(aq)


2)

As2O3(s) + NO2(g) H3AsO4(aq) + NO(g)

H3AsO4 indicates an acidic environment:

As2O3(s) + 5 H2O(l) 2 H3AsO4(aq) + 4 H+(aq) + 4 e (oxidation)

[ NO2(g) + 2 H+(aq) + 2 e NO(g) + H2O(l) ] × 2 (reduction)

Net: As2O3(s) + 2 NO2(g) + 3 H2O(l) 2 H3AsO4(aq) + 2 NO(g)

Zn(s) + BrO(aq) [Zn(OH)4]2–(aq) + Br(aq)

[Zn(OH)4]2– indicates a basic environment:

Zn(s) + 4 H2O(l) [Zn(OH)4]2–(aq) + 4 H+(aq) + 2 e (oxidation)

BrO(aq) + 2 H+(aq) + 2 e Br(aq) + H2O(l) (reduction)

Net in acid: Zn(s) + BrO(aq) + 3 H2O(l) [Zn(OH)4]2–(aq) + Br(aq) + 2 H+(aq)

Neutralization: 2 H+(aq) + 2 OH(aq) 2 H2O(l)

Net: Zn(s) + BrO(aq) + H2O(l) + 2 OH(aq) [Zn(OH)4]2–(aq) + Br(aq)


3)

HBr(aq) + MnO2(s) Br2(l) + Mn2+(aq)

HBr indicates an acidic environment:

2 HBr(aq) Br2(l) + 2 H+(aq) + 2 e (oxidation)

MnO2(s) + 4 H+(aq) + 2 e Mn2+(aq) + 2 H2O(l) (reduction)

Net: 2 HBr(aq) + MnO2(s) + 2 H+(aq) Br2(l) + Mn2+(aq) + 2 H2O(l)

[Cr(OH)4](aq) + MnO4(aq) CrO42–(aq) + MnO2(s)

[Cr(OH)4] indicates a basic environment:

[Cr(OH)4](aq) CrO42–(aq) + 4 H+(aq) + 3 e (oxidation)

MnO4(aq) + 4 H+(aq) + 3 e MnO2(s) + 2 H2O(l) (reduction)

Net in acid: [Cr(OH)4](aq) + MnO4(aq) CrO42–(aq) + MnO2(s) + 2 H2O(l)

Neutralization: none

Net: [Cr(OH)4](aq) + MnO4(aq) CrO42–(aq) + MnO2(s) + 2 H2O(l)


4)

H3AsO4(aq) + Al(s) AsH3(g) + Al3+(aq)

H3AsO4 indicates an acidic environment:

[ H3AsO4(aq) + 8 H+(aq) + 8 e AsH3(g) + 4 H2O(l) ] × 3 (reduction)

[ Al(s) Al3+(aq) + 3 e ] × 8 (oxidation)

Net: 3 H3AsO4(aq) + 8 Al(s) + 24 H+(aq) 3 AsH3(g) + 8 Al3+(aq) + 12 H2O(l)

Co(OH)2(s) + ClO2(aq) Co(OH)3(s) + ClO(aq)

Co(OH)2 and Co(OH)3 indicate a basic environment:

[ Co(OH)2(s) + H2O(l) Co(OH)3(s) + H+(aq) + e ] × 2 (oxidation)

ClO2(aq) + 2 H+(aq) + 2 e ClO(aq) + H2O(l) (reduction)

Net in acid: 2 Co(OH)2(s) + ClO2(aq) + H2O(l) 2 Co(OH)3(s) + ClO(aq)

Neutralization: none

Net: 2 Co(OH)2(s) + ClO2(aq) + H2O(l) 2 Co(OH)3(s) + ClO(aq)


5)

HClO4(aq) + Fe2+(aq) ClO3(aq) + Fe3+(aq)

HClO4 indicates an acidic environment:

HClO4(aq) + H+(aq) + 2 e ClO3(aq) + H2O(l) (reduction)

[ Fe2+(aq) Fe3+(aq) + e ] × 2 (oxidation)

Net: HClO4(aq) + 2 Fe2+(aq) + H+(aq) ClO3(aq) + 2 Fe3+(aq) + H2O(l)

Ni(OH)3(s) + ClO2(aq) Ni(OH)2(s) + ClO3(aq)

Ni(OH)3 and Ni(OH)2 indicate a basic environment:

[ Ni(OH)3(s) + H+(aq) + e Ni(OH)2(s) + H2O(l) ] × 2 (reduction)

ClO2(aq) + H2O(l) ClO3(aq) + 2 H+(aq) + 2 e (oxidation)

Net in acid: 2 Ni(OH)3(s) + ClO2(aq) 2 Ni(OH)2(s) + ClO3(aq) + H2O(l)

Neutralization: none

Net: 2 Ni(OH)3(s) + ClO2(aq) 2 Ni(OH)2(s) + ClO3(aq) + H2O(l)


6)

H2SO3(aq) + Ag(s) + Br(aq) AgBr(s) + S(s)

H2SO3 indicates an acidic environment:

H2SO3(aq) + 4 H+(aq) + 4 e S(s) + 3 H2O(l) (reduction)

[ Ag(s) + Br(aq) AgBr(s) + e ] × 4 (oxidation)

Net: H2SO3(aq) + 4 Ag(s) + 4 Br(aq) + 4 H+(aq) 4 AgBr(s) + S(s) + 3 H2O(l)

Co(OH)3(s) + NO2(aq) Co(OH)2(s) + NO3(aq)

Co(OH)3 and Co(OH)2 indicate a basic environment:

[ Co(OH)3(s) + H+(aq) + e Co(OH)2(s) + H2O(l) ] × 2 (reduction)

NO2(aq) + H2O(l) NO3(aq) + 2 H+(aq) + 2 e (oxidation)

Net in acid: 2 Co(OH)3(s) + NO2(aq) 2 Co(OH)2(s) + NO3(aq) + H2O(l)

Neutralization: none

Net: 2 Co(OH)3(s) + NO2(aq) 2 Co(OH)2(s) + NO3(aq) + H2O(l)


7)

HNO3(aq) + Hg22+(aq) Hg2+(aq) + NO(g)

HNO3 indicates an acidic environment:

[ HNO3(aq) + 3 H+(aq) + 3 e NO(g) + 2 H2O(l) ] × 2 (reduction)

[ Hg22+(aq) 2 Hg2+(aq) + 2 e ] × 3 (oxidation)

Net: 2 HNO3(aq) + 3 Hg22+(aq) + 6 H+(aq) 6 Hg2+(aq) + 2 NO(g) + 4 H2O(l)

AgO(s) + Zn(s) Ag2O(s) + Zn(OH)2(s)

Zn(OH)2 indicates a basic environment:

2 AgO(s) + 2 H+(aq) + 2 e Ag2O(s) + H2O(l) (reduction)

Zn(s) + 2 H2O(l) Zn(OH)2(s) + 2 H+(aq) + 2 e (oxidation)

Net in acid: 2 AgO(s) + Zn(s) + H2O(l) Ag2O(s) + Zn(OH)2(s)

Neutralization: none

Net: 2 AgO(s) + Zn(s) + H2O(l) Ag2O(s) + Zn(OH)2(s)


8)

NO2(g) + HCN(aq) C2N2(g) + HNO2(aq)

HCN and HNO2 indicate an acidic environment:

[ NO2(g) + H+(aq) + e HNO2(aq) ] × 2 (reduction)

2 HCN(aq) C2N2(g) + 2 H+(aq) + 2 e (oxidation)

Net: 2 NO2(g) + 2 HCN(aq) C2N2(g) + 2 HNO2(aq)

Ag2O(s) + Al(s) Ag(s) + Al(OH)3(s)

Al(OH)3 indicates a basic environment:

[ Ag2O(s) + 2 H+(aq) + 2 e 2 Ag(s) + H2O(l) ] × 3 (reduction)

[ Al(s) + 3 H2O(l) Al(OH)3(s) + 3 H+(aq) + 3 e ] × 2 (oxidation)

Net in acid: 3 Ag2O(s) + 2 Al(s) + 3 H2O(l) 6 Ag(s) + 2 Al(OH)3(s)

Neutralization: none

Net: 3 Ag2O(s) + 2 Al(s) + 3 H2O(l) 6 Ag(s) + 2 Al(OH)3(s)


9)

H2S(aq) + BrO3(aq) BrO2(g) + S(s)

H2S indicates an acidic environment:

H2S(aq) S(s) + 2 H+(aq) + 2 e (oxidation)

[ BrO3(aq) + 2 H+(aq) + e BrO2(g) + H2O(l) ] × 2 (reduction)

Net: H2S(aq) + 2 BrO3(aq) + 2 H+(aq) 2 BrO2(g) + S(s) + 2 H2O(l)

Mg(s) + ClO4(aq) Mg(OH)2(s) + ClO3(aq)

Mg(OH)2 indicates a basic environment:

Mg(s) + 2 H2O(l) Mg(OH)2(s) + 2 H+(aq) + 2 e (oxidation)

ClO4(aq) + 2 H+(aq) + 2 e ClO3(aq) + H2O(l) (reduction)

Net in acid: Mg(s) + ClO4(aq) + H2O(l) Mg(OH)2(s) + ClO3(aq)

Neutralization: none

Net: Mg(s) + ClO4(aq) + H2O(l) Mg(OH)2(s) + ClO3(aq)