Question

The $K_a$ of an acid is 3.2 $\times$ ${10}^{–5}$. The degree of dissociation of the acid at concentration of 0.2 M is

• A. $6.0\times {10}^{-2}$
• B. $1.26\times {10}^{-2}$
• C. $40\times {10}^{-4}$
• D. $0.04\times {10}^{-3}$

Answer 1

The correct option is B $1.26\times {10}^{-2}$

Degree of dissociation, $\alpha =\sqrt{\frac{K_a}{C}}$
$=\sqrt{\frac{3.2\times {10}^{-5}}{0.2}}=1.26\times {10}^{-2}$