JEE PYQ: Ionic Equilibrium Question 3
Question 3 - 2021 (17 Mar Shift 1)
Type: Numerical
(0). (01 moles of a weak acid HA $(K_a = 2.0 \times 10^{-6})$ is dissolved in 1.0 L of 0.1 M HCl 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 $\ll 1$]
Show Answer
Answer: 2
Solution
$\text{HA} \rightleftharpoons \text{H}^+ + \text{A}^-$
Initial conc: 0.01 M, 0.1 M, 0
Equil conc: $(0.01 - x) \approx 0.01$, $(0.1 + x) \approx 0.1$, $x$
$K_a = \frac{[\text{H}^+][\text{A}^-]}{[\text{HA}]} = \frac{0.1 \times x}{0.01} = 2 \times 10^{-6}$
$x = 2 \times 10^{-7}$
$\alpha = \frac{x}{0.01} = \frac{2 \times 10^{-7}}{0.01} = 2 \times 10^{-5}$
BETA
