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Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): For a given solution of a non-volatile solute, the relative lowering of vapour pressure increases with temperature, while the absolute lowering of vapour pressure remains constant. Reason (R): The vapour pressure of a pure solvent increases with temperature, while the mole fraction of the solute in

Options

  1. ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
  2. BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
  3. C(A) is correct but (R) is not correct
  4. D(A) is not correct but (R) is correct

Correct answer

D. (A) is not correct but (R) is correct

Step-by-step solution

Assertion (A) is not correct. According to Raoult's law, the relative lowering of vapour pressure ( P P^0 ) is equal to the mole fraction of the solute ( _ solute ). Since mole fraction does not depend on temperature, the relative lowering remains constant for a given solution. The absolute lowering of vapour pressure is P = P^0 _ solute . Since P^0 increases with temperature, P must increase with temperature. Reason (R) is correct. The vapour pressure of a pure solvent ( P^0 ) increases with an increase in tempera

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