Solve this following

$\mathrm{HA} \rightleftharpoons \mathrm{H}^{+}+\mathrm{A}^{-}$

Initial conc. $0.01 \mathrm{M} \quad 0.1 \mathrm{M} \quad 0$

Equ. conc. $(0.01-\mathrm{x})(0.1+\mathrm{x}) \mathrm{xM}$

$\approx 0.01 \mathrm{M} \approx 0.1 \mathrm{M}$

Now, $\mathrm{K}_{\mathrm{a}}=\frac{\left[\mathrm{x}^{+}\right]\left[\mathrm{A}^{-}\right]}{[\mathrm{HA}]} \Rightarrow 2 \times 10^{-6}=\frac{0.1 \times \mathrm{x}}{0.01}$

$\therefore \quad x=2 \times 10^{-7}$

Now, $\alpha=\frac{\mathrm{x}}{0.01}=\frac{2 \times 10^{-7}}{0.01}=2 \times 10^{-5}$