Chemistry - Electrochemistry Question with Solution | TestHub

The molar conductivity of aqueous solution of a weak acid$\text{HA}$is$\text{200}{\text{Scm}}^{\text{2}}{\text{mol}}^{-\text{1}}$and its$\text{pH}$is$\text{4}\text{.}$What is the value of${\text{pK}}_{\text{a}}$of$\text{HA}$at${\text{25}}^{\text{o}}\text{C}$?
(Given:${\text{λ}}_{\text{m}}^{\text{o}}\left(\text{NaA}\right)\text{=}\text{100}{\text{Scm}}^{\text{2}}{\text{mo1}}^{-\text{1}}\text{,}{\text{λ}}_{\text{m}}^{\text{o}}\left(\text{HCl}\right)\text{=}\text{425}{\text{Scm}}^{\text{2}}{\text{mol}}^{-\text{1}}\text{,}{\text{λ}}_{\text{m}}^{\text{o}}\text{(NaCl)}\text{=}\text{(125}{\text{Scm}}^{\text{2}}{\text{mo1}}^{-\text{1}}{\text{)λ}}_{\text{m}}^{\text{o}}\left(\text{NaA}\right)\text{=}\text{100}{\text{Scm}}^{\text{2}}{\text{mo1}}^{-\text{1}}\text{,}{\text{λ}}_{\text{m}}^{\text{o}}\left(\text{HCl}\right)\text{=}\text{425}{\text{Scm}}^{\text{2}}{\text{mol}}^{-1}\text{,}{\text{λ}}_{\text{m}}^{\text{o}}\text{(NaCl)}\text{=}\text{125}{\text{Scm}}^{\text{2}}{\text{mo1}}^{-\text{1}}\text{)}$)