Which of the following is the only incorrect information regarding the composition of the system at — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

At $P = 0.51 \text{ bar}$, $P = P_A^\circ X_A + P_B^\circ(1 - X_A) \Rightarrow 0.51 = 0.4X_A + 0.6(1 - X_A) \Rightarrow X_A = 0.45$ (Option A is correct). $Y_A = \frac{0.4 \times 0.45}{0.51} = \frac{0.18}{0.51} = \frac{6}{17}$ (Option B is correct). Using a mass balance for A: $n_L X_A + n_V Y_A = 2.0$ with $n_L + n_V = 5$. This yields $n_L(0.45) + (5 - n_L)(\frac{6}{17}) = 2.0$, leading to $n_L = \frac{80}{33}$. Thus, $n_{A(\text{liquid})} = n_L X_A = \frac{80}{33} \times 0.45 = \frac{12}{11}$ (Option C is correct). Moles of A in vapour = Total A - $n_{A(\text{liquid})} = 2.0 - \frac{12}{11} = \frac{10}{11}$. Option D claims it is $\frac{12}{11}$, making it the only incorrect statement. Therefore, correct answer is D.