Question

E.M.F. of $Ni(s)\left|N{i}^{2+}(aq)\Vert C{u}^{2+}(aq)\right|Cu(s)$ cell can be increased by

• A. Adding $N{H}_3$ in the right half-cell
• B. Increasing the conc. of $N{i}^{2+}$ ions
• C. Adding dimethyl glyoxime into the left half-cell
• D. Changing the electrolyte present in salt bridge

Answer 1

Answer: (C)

$Ni+C{u}^{+2}⟶Cu+N{i}^{+2}$
$E=E^{\circ }+\frac{0.059}{2}\log \frac{[Ni]\left[C{u}^{+2}\right]}{[Cu]\left[N{i}^{+2}\right]}$
(1) $C{u}^{+2}+4N{H}_3⟶{\left[Cu{\left(N{H}_3\right)}_4\right]}^{+2}$
i.e., Concentration of $C{u}^{+2}$ decreases which decreases (E)
(2) $\left(N{i}^{+2}\right)$ increases $\to E$ decreases

i.e., concentration of $N{i}^{+2}$ decreases $\to E_{\text{cell }}$ increases