AIPMT MAINS 2012 Chemistry Raoult's Law MCQ Question
Vapour pressure of chloroform (CHCl₃) and dichloromethane (CH₂Cl₂) at 25°C are 200 mm Hg and 41.5 mm Hg respectively. Vapour pressure of the solution obtained by mixing 25.5 g of CHCl₃ and 40 g of CH₂Cl₂ at the same temperature will be: (Molecular mass of CHCl₃ = 119.5 u and molecular mass of CH₂Cl₂ = 85 u).
173.9 mm Hg
615.0 mm Hg
347.9 mm Hg
285.5 mm Hg
Correct Answer
This question was cancelled by the examination board. Full marks are awarded to every candidate.
Detailed Explanation
The vapour pressure of the solution is calculated using Raoult's law: P_T = P_A^0 X_A + P_B^0 X_B. The mole fractions are calculated as n_CHCl₃ = 25.5/119.5 = 0.213 and n_CH₂Cl₂ = 40/85 = 0.47. Substituting these values gives P_T = 90.92 mm Hg.
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