Question

Which of the following statement is not correct?

• A. Vapour pressure increases with decrease in polarity of the solvent
• B. Vapour pressure increases with increase in temperature
• C. Solvent with high boiling point has higher vapour pressure
• D. Heavier solvents of same polarity have lower vapour pressure

Hint:

Higher boiling point means stronger intermolecular forces and lower vapour pressure.

Answer 1

The Correct Option is C

Step 1: Understand vapour pressure concept.
Vapour pressure depends on intermolecular forces: stronger intermolecular forces lead to lower vapour pressure, while weaker forces lead to higher vapour pressure.

Step 2: Analyze statement (1).
Lower polarity means weaker intermolecular forces, so molecules escape more easily into vapour phase. Hence vapour pressure increases. Statement (1) is correct.

Step 3: Analyze statement (2).
As temperature increases, kinetic energy increases, so more molecules overcome intermolecular forces. Therefore vapour pressure increases. Statement (2) is correct.

Step 4: Analyze statement (3).
A high boiling point indicates strong intermolecular forces. Strong forces actually mean LOW vapour pressure, not high. Hence statement (3) is incorrect.

Step 5: Analyze statement (4).
Heavier molecules have stronger dispersion forces, so vapour pressure decreases. Statement (4) is correct.

Step 6: Final conclusion.
Thus incorrect statement is: \[ \boxed{(3)} \]