Question

Assertion: When methyl alcohol is added to water, boiling point of water increases.

Reason: When a volatile solute is added to a volatile solvent, an elevation in the boiling point is observed.

• A. Assertion is a correct statement but the reason is a wrong statement.
• B. Assertion and reason both are correct statements but the reason is not the correct explanation for assertion.
• C. Assertion and reason both are incorrect statements.
• D. Assertion and reason both are correct statements and reason is the correct explanation for assertion.
• E. Assertion is a wrong statement but the reason is a correct statement.

Answer 1

The correct option is C

Assertion and reason both are incorrect statements.

Analysing the assertion :

Methyl alcohol and water both are volatile liquids which when mixed forms a binary solution.

The vapour pressure of this solution becomes more as compared to individual pure components because when methyl alcohol is added to water, methyl alcohol-water interaction is less than that of methyl alcohol-methyl alcohol or water-water interaction that is why it will show positive deviation from Raoult's law.

Since a positive deviation from Raoult's law indicates a rise in vapour pressure the boiling point of the solution decreases. So, the assertion is incorrect.

Analysing the reason :

When a volatile solute is added to a volatile solvent, the vapour pressure of the solvent increases, which decreases the boiling point.

So, when a volatile solute is added to a volatile solvent, an elevation in the boiling point is not observed.

Hence, the reason is incorrect.

So, both the assertion and the reason are incorrect statements.

Hence, option (D) is the correct answer.