COMEDK · Chemistry · 17. Solutions

At 300 K the vapour pressure of an ideal solution containing 1.0 mole each of volatile liquids X and Y is 1000 mm . Keeping the temperature constant, when 2.0 moles of liquid X is added to the solution, its vapour pressure increases by 200 mm . Calculate the vapour pressure of X and Y in their pure state

A \(P_X^0=1200 \quad P_Y^0=480\)
B \(P_X^0=1400 \quad P_Y^0=600\)
C \(P_X^0=1700 \quad P_Y^0=400\)
D \(P_X^0=1000 \quad P_Y^0=500\)

Verified Solution

Answer & Solution

Correct Answer

(B) \(P_X^0=1400 \quad P_Y^0=600\)

Step-by-step Solution

Detailed explanation

Let \(P_X^0\) and \(P_Y^0\) be the vapour pressures of pure liquids X and Y respectively. According to Raoult's law, the total vapour pressure \(P_{total}\) is given by \(P_{total} = x_X P_X^0 + x_Y P_Y^0\). For the initial solution containing 1.0 mole of X and 1.0 mole of Y,…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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