Question

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

• A. Adding $NH _{3}$ in the right half-cell
• B. Increasing the conc. of $Ni ^{2+}$ ions
• C. Adding dimethyl glyoxime into the left half-cell
• D. Changing the electrolyte present in salt bridge

Answer 1

Answer: (C)

$Ni + Cu ^{+2} \longrightarrow Cu + Ni ^{+2} $
$E = E ^{\circ}+\frac{0.059}{2} \log \frac{[ Ni ]\left[ Cu ^{+2}\right]}{[ Cu ]\left[ Ni ^{+2}\right]}$
(1) $Cu ^{+2}+4 NH _{3} \longrightarrow \left[ Cu \left( NH _{3}\right)_{4}\right]^{+2}$
i.e., Concentration of $Cu ^{+2}$ decreases which decreases (E)
(2) $\left( Ni ^{+2}\right)$ increases $\rightarrow E$ decreases

i.e., concentration of $Ni ^{+2}$ decreases $\rightarrow E _{\text {cell }}$ increases