Chapter 20, Problem 70A

(a)

Interpretation Introduction

Interpretation:

The reactions occurring at anode and cathode are to be written.

Concept introduction:

A fuel cell converts chemical energy into electrical energy. A hydrogen fuel cell uses hydrogen and oxygen gas as fuel and produces water electricity and heat.

Answer to Problem 70A

Reaction at anode:

${\text{ 2H}}_{\text{2}}\to {\text{4H}}^{\text{+}}{\text{+4e}}^{\text{–}}$

Reaction at cathode:

${\text{O}}_{\text{2}}{\text{+4H}}^{\text{+}}{\text{+4e}}^{\text{–}}\to {\text{2H}}_{\text{2}}\text{O}$

Explanation of Solution

In the hydrogen fuel cell hydrogen gas gets converted to hydrogen ions in the presence of catalyst so it acts as an anode. Oxygen gas at the cathode reacts with the hydrogen ions to form water and release energy.

Interpretation Introduction

(b)

Interpretation:

The standard cell potential for the fuel cell is to be calculated.

Concept introduction:

Standard cell potential of a cell is the sum of its oxidation and reduction potential of its half cells.

Answer to Problem 70A

The standard cell potential is 1.23V.

Explanation of Solution

The potential of reduction half cell=1.23V

The potential of oxidation half cell=0V

Standard cell potential=1.23+0=1.23V