Homework
Chapter 19


Homework 19.1

1. Assign the correct oxidation number to the individual atom or ion in the following:
a) Mn in MnO2
b) S in S8
c) Cl in CaCl2
d) I in IO3-1
e) C in HCO3-1
f) Fe in Fe2(SO4)3
g) S in Fe2(SO4)3
h) P in PO4-3
i) Mn in MnO4-1
j) Cl in ClO3-1
k) N in NO2
l) N in N2O4

Homework 19.2

1. Correctly balance the following redox reactions showing the oxidation numbers for each substance that changes oxidation state:

a) Mg + ZnCl2 ---> Zn + MgCl2

b) H2 + OF2 ---> H2O + HF

c) CH4 + O2 ---> CO2 + H2O

d) SbCl5 + KI ---> KCl + I2 + SbCl3

e) Ca(OH)2 + NaOH + ClO2 + C ---> NaClO2 + CaCO3 + H2O

f) HNO3 + H2S ---> NO + H2O + S

g) CuS + HNO3 ---> Cu(NO3)2 + NO + S + H2O

h) K2Cr2O7 + HI ---> CrI3 + KI + I2 + H2O

Homework 19.3

1. Describe the chemical activity of the alkali metals on the basis of oxidizing and reducing strength.

2. Describe the chemical activity of the halogens on the basis of oxidizing and reducing strength.

3. Using table 19-3 in your text, indicate if Cl2 would be reduced by I-1. Explain your answer based on the table.

4. Which is the stronger oxidizing agent
a) Cu+2 or Al+3
b) H2 or H3O+1
c) Cr or Cu
d) Ag+1 or Na+1
e) Fe+3 or Fe+2

5. For each of the following incomplete reactions, state whether a redox reaction is likely to occur, using table 19-3:
a) Mg + SN+2 --->
b) Ag + Cu+2 --->
c) Br2 + I-1 --->

Homework 19.4

1. What are the differences between a voltaic cell and an electrolytic cell.

2. In the process of electroplating, describe

a) the cathode material and the solution into which the cathode dips and

b) the anode material and the solution into which the anode dips.

3. What is a rechargeable cell?

4. Describe the structure and purpose of SHE.

5.Define the standard electrode potential.

6. Given the Na+1/Na and K+1/K half cells use table19-4 on p 615) determine the overall electrochemical reaction that proceeds spontaneously and the Eo value.

7. Given the Cu2+/Cu and Ag+/Ag half cells use table19-4 on p 615) determine the overall electrochemical reaction that proceeds spontaneously and the Eo value.

8. Given the Na+/Na and Ni2+/Ni half cells use table19-4 on p 615) determine the overall electrochemical reaction that proceeds spontaneously and the Eo value.

9. If a strip of Ni were dipped into a solution of AgNO3, what would be expected to occur. Explain using Eo values and equations.



Answers to Balancing Redox Reactions Homework


a) Mg + ZnCl2 ---> Zn + MgCl2

b) 2 H2 + OF2 ---> H2O + 2 HF

c) CH4 + 2 O2 ---> CO2 + 2 H2O

d) SbCl5 + 2 KI ---> 2 KCl + I2 + SbCl3

e) Ca(OH)2 +
4 NaOH +4 ClO2 + C ---> 4 NaClO2 + CaCO3 + 3 H2O

f) 2 HNO3 + 3 H2S ---> 2 NO + 4 H2O + 3 S

g) 3 CuS + 8 HNO3 ---> 3 Cu(NO3)2 + 2 NO + 3 S + 4 H2O

h) K2Cr2O7 +
14 HI ---> 2 CrI3 + 2 KI + 3 I2 + 7 H2O