QJEEM20Chc12e: JEE Main 2020 Chemistry - Class 12 JEEM20Chc12e Solution: For an electrochemical cell Sn(s)

Cell reaction is :

Sn(s) + Pb⁺²(aq) $\to$ Sn⁺²(aq) + Pb(s)

Apply Nernst equation :

E_cell = $E_{cell}^0$ - ${{0.06} \over 2}\log {{\left[ {S{n^{ + 2}}} \right]} \over {\left[ {P{b^{ + 2}}} \right]}}$ ....(1)

$\Rightarrow$ $E_{cell}^0$ = -0.13 + 0.14 = 0.01 V

At equilibrium : E_cell = 0

Substituting in (1), we get

0 = 0.01 - ${{0.06} \over 2}\log {{\left[ {S{n^{ + 2}}} \right]} \over {\left[ {P{b^{ + 2}}} \right]}}$

$\Rightarrow$ $\log {{\left[ {S{n^{ + 2}}} \right]} \over {\left[ {P{b^{ + 2}}} \right]}}$ = ${1 \over 3}$

$\Rightarrow$ ${{\left[ {S{n^{2 + }}} \right]} \over {\left[ {P{b^{2 + }}} \right]}}$ = 2.15