Chapter 19, Problem 19.161MP

Interpretation Introduction

(a)

Interpretation:

A balanced equation for the cell reaction should be written.

Concept introduction:

To obtain the cell reaction, cathode reaction and the anode reaction should be added together and before that, the two half-cell reactions should be electronically equal, so that the electrons are cancelled off when adding. If common ions present they should also be deducted.

Interpretation Introduction

(b)

Interpretation:

The value of E⁰ and the equilibrium constant K for the cell reaction at 25⁰ C should be calculated. Whether E⁰ and K increase, decrease or remain the same on raising temperature should be determined.

Concept introduction:

The standard Gibbs free energy change can be calculated as follows:

$\Delta G^0={\displaystyle \sum \Delta G_f^0\left(\text{Products}\right)-{\displaystyle \sum \Delta G_f^0\left(\text{Reactants}\right)}}$

$\begin{array}{l}\Delta G^0=-nF{E}^0\\ \\ \Delta G^0=\text{ Standard Gibbs free energy}\\ \text{n = number of moles of electrons transferred}\\ \text{F = Faraday constant}\\ {\text{E}}^0=\text{ Standard cell potential}\end{array}$

$\begin{array}{l}\Delta G^0=-RT\ln K\\ \\ \Delta G^0=\text{ Standard Gibbs free energy}\\ \text{R = Universal gas constant}\\ \text{T = Absolute temperature}\\ \text{K = Equilibrium constant}\end{array}$

Interpretation Introduction

(c)

Interpretation:

Number of grams of butane required to produce a constant current of 10.5 A for 8.00 h should be calculated. Number of liters of gaseous butane at 20⁰ C and 815 mmHg pressure required should be calculated.

Concept introduction:

The number of coulombs of charge passed through the cell equals the product of the current in amperes and the time in seconds.

$\text{Charge (C) = Current (A) }\times \text{ Time (s)}$

$\begin{array}{l}PV=nRT\\ P=\text{pressure}\\ \text{V= volume}\\ \text{n = number of moles}\\ \text{R = universal gas constant}\\ \text{T =absolute temperature}\end{array}$