The molar ratio of dimer to monomer for acetic acid in benzene is equal to — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

Let the equilibrium monomer concentration be $x$ and dimer be $y$. We have $x + 2y = 0.1\text{ M}$. In benzene, the equilibrium constant $K = \frac{y}{x^2} = 150 \implies y = 150x^2$. Substituting this into the mass balance: $x + 300x^2 = 0.1$. Solving the quadratic equation $300x^2 + x - 0.1 = 0$ yields $x = 1/60\text{ M}$. The dimer concentration $y = 150(1/60)^2 = 150 / 3600 = 1/24\text{ M}$. The molar ratio of dimer to monomer is $y/x = (1/24) / (1/60) = 60/24 = 5/2$. Therefore, correct answer is C.