(d)
By Nernst equation,
$E_{cell} = \ E_{cell}^{{^\circ}}\ - \ \frac{2.303\ RT}{nF}\log_{10}K$
At equilibrium $E_{cell}$ =0
Given that,
$\therefore R\ = 8.315\ JK^{- 1}\ {mol}^{- 1}$
$T\ = \ 25\ ℃\ + \ 273\ = \ 298K$
$F\ = \ 96500\ C\ and\ n\ = \ 2$
$\therefore\ \ \ \ \ \ E_{cell}^{{^\circ}}\ = \ \ \frac{2.303\ \times 8.314\ \times 298}{2\ \times 96500}\ \log_{10}K$
$= \ \frac{0.0591}{2\ }\ \log_{10}K$
∵ Given that $E_{cell}^{{^\circ}}\ = \ 0.295\ V$
∴ $0.295\ = \ \frac{0.0591}{2\ }\ \log_{10}K$
$\log_{10}K\ = \ \ \frac{0.295\ \times 2}{0.0591}\ = \ 10$
$\log_{10}K\ = \ antilog\ 10$
$K\ = \ 1\ \times \ 10^{10}$