The molar conductance of a 0.01 M solution of acetic acid was found to be at 25°C. The ionic conduct — Electrochemistry Chemistry Question
Question
The molar conductance of a 0.01 M solution of acetic acid was found to be $16.30\ \Omega^{–1}\text{ cm}^{–1}\text{ mol}^{–1}$ at 25°C. The ionic conductances of hydrogen and acetate ions at infinite dilution are 349.8 and 40.9 $\Omega^{–1}\text{ cm}^{–1}\text{ mol}^{–1}$, respectively, at the same temperature. What percentage of acetic acid is dissociated at this concentration?
Answer: B
💡 Solution & Explanation
Molar conductance at infinite dilution $\Lambda_m^\circ = \lambda^\circ_{H^+} + \lambda^\circ_{CH_3COO^-} = 349.8 + 40.9 = 390.7\ \Omega^{–1}\text{cm}^2\text{mol}^{–1}$. Degree of dissociation $\alpha = \Lambda_m / \Lambda_m^\circ = 16.30 / 390.7 \approx 0.04172$. Percentage dissociation = $0.04172 \times 100 = 4.172\%$. Therefore, correct answer is B.
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