Benzene and toluene form two ideal solutions A and B at 313 K, Solution A (total pressure PA) contains equal mole of toluene and benzene. Solution B contains equal masses of both (total pressure PB). The vapour pressure of benzene and toluene are 160 and 60 mm of Hg respectively at 313 K. Calculate the value of (Round-off the answer).

# Benzene and toluene form two ideal solutions A and B at 313 K, Solution A (total pressure PA) contains equal mole of toluene and benzene. Solution B contains equal masses of both (total pressure PB). The vapour pressure of benzene and toluene are 160 and 60 mm of Hg respectively at 313 K. Calculate the value of (Round-off the answer).

1. A 2. B 3. C 4. D Fill Out the Form for Expert Academic Guidance!l

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### Solution:

Concept-  For solution A, toluene and benzene have the identical mole fractions, or 0.5 in each case.
Toluene has the following partial pressure in a vapour phase: Here, XT stands for the mole fraction of toluene in the liquid phase, while stands for the vapour pressure of pure toluene.
Now, the partial pressure of benzene in a vapour phase is: In this case, XB stands for the mole fraction of pure benzene in the liquid phase, and stands for the vapour pressure of pure benzene.
Therefore, total pressure in case of solution A becomes: The toluene and benzene masses in solution B are equal.
Toluene has a molar mass of 92.14 g/mol and benzene has a molar mass of 78.11 g/mol.
Let's assume that the solution mixture contains 78.11 g of benzene and 78.11 g of toluene.
This equates to 0.847 moles of toluene and 1 mole of benzene.
Toluene has a mole fraction of 0.4588 and benzene has a mole fraction of 0.5412.
Toluene has the following partial pressure in the vapour phase: Here, XT stands for the mole fraction of toluene in the liquid phase, while stands for the vapour pressure of pure toluene.
Benzene's partial pressure in the vapour phase is: Here, the terms XB, or the mole fraction of benzene in the liquid phase, and , or the vapour pressure of pure benzene, are used.
As a result, the overall pressure is: Thus, the value of ratio i.e Hence, the correct answer is option (1).

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