JEE MAIN - Chemistry (2012 - No. 6)
The pH of a 0.1 molar solution of the acid HQ is 3. The value of the ionization constant, Ka of this acid is :
3 $$\times$$ 10–1
1 $$\times$$ 10–3
1 $$\times$$ 10–5
1 $$\times$$ 10–7
Explication
$${H^ + } = C\alpha ;\alpha = {{\left[ {{H^ + }} \right]} \over C}$$
or $$\,\,\,\alpha = {{{{10}^{ - 3}}} \over {0.1}} = {10^{ - 2}}$$
$$Ka = C{\alpha ^2} = 0.1 \times {10^{ - 2}} \times {10^{ - 2}}$$
$$ = {10^{ - 5}}$$
or $$\,\,\,\alpha = {{{{10}^{ - 3}}} \over {0.1}} = {10^{ - 2}}$$
$$Ka = C{\alpha ^2} = 0.1 \times {10^{ - 2}} \times {10^{ - 2}}$$
$$ = {10^{ - 5}}$$