Multiple choice

When $45 gm $ of a solute is added ton $900 gm$ of water, its vapour pressure decreased from $30mm$ to $24mm$. The mole fraction of the solvent in the solution is?

  1. $0.2$
  2. $0.8$
  3. $0.1$
  4. $0.9$
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B Correct answer
Explanation

According to Raoult's Law, the vapour pressure of a solution is equal to the mole fraction of the solvent multiplied by the vapour pressure of the pure solvent. Substituting the given values, 24 = X_solvent * 30, which gives a solvent mole fraction of 0.8.

AI explanation

The relative lowering of vapour pressure is equal to the mole fraction of the solute according to Raoult's law. This gives the mole fraction of the solute as (30 minus 24) divided by 30, which equals 6 divided by 30, or 0.2. The question asks for the mole fraction of the solvent, which is 1 minus the mole fraction of the solute, so 1 minus 0.2 equals 0.8. The result is 0.8.

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