Question

How much must be a 0.02M solution of sodium acetate be diluted at ${25}^{\circ }C$ in order to double the degree of hydrolysis?

• A. 0.25 times
• B. 2 times
• C. 4 times
• D. 8 times

Answer 1

The correct option is C

4 times

Let 'h' be the initial degree of hydrolysis

$K_h=C{h}^2=0.2h^2\to \left(i\right)$

The concentration becomes $C_1$ when degree of hydrolysis is $2h,K_h^{\prime }=C_1(2h{)}^2=4C_1{h}^2\to (ii)$

Dividing Eqs (i) by (ii)

$\frac{K_h}{K_h^{\prime }}=\frac{0.2h^2}{4C_{1}h2};1=\frac{0.2}{4C_1}$

$C_1=\frac{0.2}{4}=0.05M$

Now, from $M_1{V}_1=M_2{V}_2$

$0.2V_1=0.05V_2$

$\Rightarrow V_2=\frac{0.2}{0.05}{V}_1=4V_1$

Therefore, the solution a must be diluted four times