Question

$0.01$ moles of a weak acid $HA\left(K_a=2.0\times 10^{-6}\right)$ is dissolved in $1.0L$ of $0.1MHCl$ solution. The degree of dissociation of $HA$ is ________ $\times 10^{-5}$ (Round off to the Nearest Integer). [Neglect volume change on adding HA. Assume degree of dissociation $<<1]$

Answer 1

Answer: 2

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

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

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