Question

(a) The conductivity of 0.001 mol L${}^{-1}$ solution of $C{H}_{3}COOH$ is 3.905$\times {10}^{-5}$ Scm${}^{-1}$. Calculate its molar conductivity and degree of dissociation.
Given: $\left(H^{+}\right)$= 349.6 S $c{m}^{2}mo{l}^{-1}$ and $\left(C{H}_{3}CO{O}^{-}\right)$= 40.9S $c{m}^{2}mo{l}^{-1}$.
(b) Define electro chemical cell. What happens if external potential applied becomes greater than $E_{cell}$ of electro chemical cell?

Answer 1

(a) The conductivity, $\kappa =3.905\times {10}^{-5}S/cm$
The concentration, $C=0.001M$
The molar conductivity at given concentration, $\Lambda =\frac{1000\kappa }{C}=\frac{1000\times 3.905\times {10}^{-5}}{0.001}=39.05Sc{m}^2/mol$
At infinite dilution, the molar conductivity,
${\Lambda }_0={\Lambda }_{H+}+{\Lambda }_{CH3CO{O}^{-}}$
${\Lambda }_0=349.6+40.9=390.5Sc{m}^2/mol$
The degree of dissociation, $\alpha =\frac{\Lambda }{{\Lambda }_0}=\frac{39.05}{390.5}=0.1$
(b) An electrochemical cell is a device which is used to study the chemical reactions electrically. It consists of two electronic conductors such as metal plates or carbon rods dipped into an electrolytic or ionic conductor which is an aqueous electrolyte solution or a pure liquid of an electrolyte.
Thus, electrochemical cell is a device in which the decrease of free energy during an indirect redox reaction is made to convert chemical energy into electrical energy.
If applied external potential becomes greater than $E_{cell}$ of electrochemical cell, then the electrochemical cell behaves as electrolytic cell. All the chemical reactions will be reversed and electrical energy will be converted into chemical energy.