A solution contains 4.25 g ammonia per 250.0 ml of solution. Electrical conductivity measurement at — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

Molar mass of $\text{NH}_3 = 17 \text{ g/mol}$. Moles of $\text{NH}_3 = 4.25 \text{ g} / 17 \text{ g/mol} = 0.25 \text{ mol}$. Concentration $C = 0.25 \text{ mol} / 0.25 \text{ L} = 1.0 \text{ M}$. Degree of dissociation $\alpha = 0.40\% = 0.004$. $[OH^-] = C\alpha = 1.0 \times 0.004 = 4 \times 10^{-3} \text{ M}$. $pOH = -\log(4 \times 10^{-3}) = 3 - 2\log 2 = 3 - 0.6 = 2.4$. $pH = 14 - pOH = 14 - 2.4 = 11.6$. Therefore, correct answer is A.