A $$0.004 M$$  solution of $$N{a_2}S{O_4}$$  is isotonic with $$0.010 M$$  solution of glucose at same temperature. The percentage dissociation of $$N{a_2}S{O_4}$$  is

Solution :
NOTE : For isotonic solutions, osmotic pressure is same.
$$\mathop {N{a_2}3{O_4}}\limits_{\left( {0.004\, - \,x} \right)} \,\,\,\,\,\,\,\,\,\, \rightleftharpoons \mathop {2N{a^ + }}\limits_{2x} + \mathop {SO_4^{2 - }}\limits_x $$
$${\text{Since both solutions are isotonic,}}$$
$${\text{therefore, }}0.004 + 2x\, = 0.01;$$      $${\text{ }}x = 3 \times {10^{ - 3}}$$
$$\therefore \,\,\% \,{\text{Dissociation = }}\frac{{3 \times {{10}^{ - 3}}}}{{0.004}} \times 100$$        $$ = 75\% $$