Question

Which of the following will form a cell with the highest voltage?
(a) 0.1 M Ag⁺, 2 MCo²⁺
(b) 2 M Ag⁺, 0.1 MCo²⁺
(c) 1 M Ag⁺, 1 M Co²⁺
(d) 2 M Ag⁺, 2 M Co²⁺

Answer 1

we have to check which of the following will form a cell with highest voltage.

(a) 0.1 M Ag⁺, 2 MCo²⁺

(b) 2 M Ag⁺, 0.1 MCo²⁺

(c) 1 M Ag⁺, 1 M Co²⁺

(d) 2 M Ag⁺, 2 M Co²⁺

solution : The cell reaction is given by,

$2Ag^++Co\rightarrow 2Ag+Co^{2+}$

from Nernst equation,

$\quad E=E_0+\frac{0.059}{2}\log\left(\frac{[Ag^+]}{[Co^{2+}]}\right)$

from the given equation it is clear that emf (voltage) of cell will be highest only if concentration of [Ag⁺] is highest and concentration of [Co⁺⁺] becomes is lowest.

only option (b) satisfies the given above condition. Therefore option (b) is correct choice