A cylinder fitted with a movable piston contains liquid water in equilibrium with water vapour at 25 — Chemical Equilibrium Chemistry Question
Question
A cylinder fitted with a movable piston contains liquid water in equilibrium with water vapour at 25°C. Which operation results in a decrease in the equilibrium vapour pressure?
Answer: D
💡 Solution & Explanation
The equilibrium vapour pressure of a liquid depends only on the temperature and the nature of the liquid. Changing the volume (piston) or removing liquid/vapour will momentarily disturb the system, but the equilibrium vapour pressure will remain the same. Adding a non-volatile solute like salt lowers the vapour pressure according to Raoult's Law. Therefore, correct answer is D.
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