Chapter 14, Problem 14.51P

Interpretation Introduction

Interpretation:

${\text{K}}_{\text{a}}$ value of the given reaction has to be calculated.

Concept introduction:

Nernst equation can be used to determine the cell potential at any instant, the difference from the standard state.

${\text{E}}_{\text{cell}}{\text{ = E}}_{\text{cell}}^{\text{o}}\text{ - }\left(\frac{\text{RT}}{\text{nF}}\right)\text{lnQ}$

Where:

${\text{E}}_{\text{cell}}$ = cell potential under nonstandard conditions

$\text{E}{}_{\text{cell}}^{\text{o}}$ = cell potential under standard conditions

R = gas constant, which is $\text{8}\text{.31 }\left(\text{volt-coulomb}\right)\text{/}\left(\text{mol-K}\right)$

T = temperature (kelvin), which is generally $\text{298°K }\left(\text{77°F/25°C}\right)$

n = number of moles of electrons exchanged in the electrochemical reaction

F = Faraday's constant, $\text{96500 coulombs/mol}$

Q = reaction quotient, which is the equilibrium expression with initial concentrations rather than equilibrium concentrations