Question

Equivalent conductance of 0.1 M HA (weak acid) solution is 10 $Scm^{2}$ equivalent $^{- 1}$ and that at infinite dilution is 200 $Scm^{2}$ equivalent $^{- 1}$ . Hence pH of HA solution is

• A. 1.3
• B. 1.7
• C. 2.3
• D. 3.7

Answer 1

Answer: (C)

$\alpha =\frac{\Lambda}{\Lambda_{\in fty}}=\frac{10}{200}=\frac{1}{20}$
$\text{[H}^{\text{+}} \text{]}_{\text{weak} \, \text{acid}} \, \text{=} \, \text{Cα}$
$=0.1\times \left(\frac{1}{20}\right)=5\times 10^{- 3}$
$pH=3-log5=2.3$