Electrochemistry

The resistance of \(0.1 \mathrm{~M}\) weak acid \(\mathrm{H} A\) in a conductivity cell is \(2 \times 10^3 \mathrm{~Ohm}\). The cell constant of the cell is \(0.78 ~\mathrm{C} \mathrm{~m}^{-1}\) and \(\lambda_{\mathrm{m}}^{\circ}\) of acid \(\mathrm{H} A\) is \(390 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}\). The \(\mathrm{pH}\) of the solution is