Embibe Experts Solutions for Chapter: Electrochemistry, Exercise 4: EXERCISE-4

$100 {\mathrm{mLCuSO}}_4$ (aq) was electrolyzed using inert electrodes by passing $0.965 \mathrm{A}$ till the $\mathrm{pH}$ of the resulting solution was $1$ . The solution after electrolysis was neutralized, treated with excess $\mathrm{KI}$ and titrated with $0.04 \mathrm{M} {\mathrm{Na}}_2{ \mathrm{S}}_2{\mathrm{O}}_3$. Volume of ${\mathrm{Na}}_2{ \mathrm{S}}_2{\mathrm{O}}_3$ required was $35 \mathrm{mL}$. Assuming no volume change during electrolysis, calculate:
(a) duration of electrolysis if current efficiency is $80\%$
(b) initial concentration $\left(\mathrm{M}\right)$ of ${\mathrm{CuSO}}_4$

Calculate the equilibrium concentration of all ions in an ideal solution prepared by mixing $25.00 \mathrm{mL}$ of $0.100 \mathrm{M} {\mathrm{Tl}}^{+}$ with $25.00 \mathrm{mL}$ of $0.200 \mathrm{M} {\mathrm{Co}}^{3+}$.$\mathrm{E}°\left(\frac{{\mathrm{Tl}}^{+}}{{\mathrm{Tl}}^{3+}}\right)=-1.25 \mathrm{V},\mathrm{E}°\left(\frac{{\mathrm{Co}}^{3+}}{{\mathrm{Co}}^{2+}}\right)=1.84 \mathrm{V}$

Determine at $298$ for cell :
$\mathrm{Pt}\left|\mathrm{Q},{\mathrm{QH}}_2,{\mathrm{H}}^{+}\right|\left|1\mathrm{MKCl}\right|{\mathrm{Hg}}_2{\mathrm{Cl}}_2\left|\mathrm{Hg}\right(\mathrm{l}\left)\right|\mathrm{Pt}$
(a) it's emf when $\mathrm{pH}=5.0$
(b) the $\mathrm{pH}$ when ${\mathrm{E}}_{\text{cell }}=0$
(c) the positive electrode when $\mathrm{pH}=7.5$
given ${\mathrm{E}}_{\mathrm{RP}\left(\mathrm{RHS}\right)}°=0.28,{\mathrm{E}}_{\mathrm{RP}\left(\text{ LHS }\right)}°=0.699$

Carefully observe the given figure and using data provided find the EMF of shown Galvenic cell in volt :

Solution $\mathrm{A}$ is $0.1 \mathrm{M}$ each in ${\mathrm{NH}}_4\mathrm{OH}$ and ${\mathrm{NH}}_4\mathrm{Cl}$ and solution $\mathrm{B}$ is $0.1 \mathrm{M}$ each in ${\mathrm{CH}}_3\mathrm{COOH}$ and ${\mathrm{CH}}_3{\mathrm{COO}}^{-}{\mathrm{Na}}^{+}.$
[Given : ${\mathrm{K}}_{\mathrm{a}}\left({\mathrm{CH}}_3\mathrm{COOH}\right)={10}^{-5},{ \mathrm{K}}_{\mathrm{b}}\left({\mathrm{NH}}_4\mathrm{OH}\right)={10}^{-5}$ and $\frac{2.303\mathrm{RT}}{\mathrm{F}}=0.06$ volt]

Dal lake has water $8.2\times {10}^{12}$ litre approximately. A power reactor produces electricity at the rate of $1.5\times {10}^6$ coulomb per second at an appropriate voltage. How many years would it take to electrolyse the lake?

Calculate the cell potential of a cell having reaction ${\mathrm{Ag}}_2 \mathrm{S}+2e^{-}\rightleftharpoons 2\mathrm{Ag}+{\mathrm{S}}^{2-}$ in a solution buffered at $\mathrm{pH}=3$ and which is also saturated with $0.1 \mathrm{M} {\mathrm{H}}_2 \mathrm{S}$.
For ${\mathrm{H}}_2 \mathrm{S}:{\mathrm{K}}_1={10}^{-8}$ and ${\mathrm{K}}_2=1.1\times {10}^{-13},{ \mathrm{K}}_{\mathrm{sp}}\left({\mathrm{Ag}}_2 \mathrm{S}\right)=2\times {10}^{-49},{\mathrm{E}}_{{\mathrm{Ag}}^{+}/\mathrm{Ag}}°=0.8$.

Calculate the solubility and solubility product of ${\mathrm{Co}}_2\left[\mathrm{Fe}(\mathrm{CN}{)}_6\right]$ in water at $25°\mathrm{C}$ from the following data : Conductivity of a saturated solution of ${\mathrm{Co}}_2\left[\mathrm{Fe}(\mathrm{CN}{)}_6\right]$ is $2.06\times {10}^{-6}{\mathrm{\Omega }}^{-1}{ \mathrm{cm}}^{-1}$ and that of water used $4.1\times {10}^{-7}{\mathrm{\Omega }}^{-1}{ \mathrm{cm}}^{-1}$. The ionic molar conductivities of ${\mathrm{Co}}^{2+}$ and $\mathrm{Fe}(\mathrm{CN}{)}_6^{4-}$ are $86.0 {\mathrm{\Omega }}^{-1}{ \mathrm{cm}}^2{ \mathrm{mol}}^{-1}$ and $444.0 {\mathrm{\Omega }}^{-1}{ \mathrm{cm}}^{-1}{ \mathrm{mol}}^{-1}$