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The pressure exerted by the vapour of a liquid at a particular temperature is known as the vapour…
The pressure exerted by the vapour of a liquid at a particular temperature is known as the vapour pressure of the liquid at that temperature. When a non-volatile solute such as glucose is added to a volatile solvent like water, the vapour pressure of the solution decreases. F. Raoult (1887), a French chemist, studied the vapour pressure of several solutions. According to him, the vapour pressure of a solution depends on the temperature. A prior knowledge of the boiling points of different liquids helps in understanding their vapour pressure in solution.
Answer the following questions.
(a)[1.0]
Write the Raoult’s law for a solution containing a non-volatile solute.
(b)[1.0]
What is an ideal solution and a non-ideal solution?
(c)[2.0]
Calculate the vapour pressure of a solution containing $2\text{ moles}$ of glucose ($\text{C}_6\text{H}_{12}\text{O}_6$) in $900\text{ g}$ of water if the vapour pressure of pure water is $4\cdot60\text{ mm of Hg}$.
(Given: Atomic weight of $\text{C} = 12$, $\text{H} = 1$ and $\text{O} = 16$)
(d)[1.0]
Two liquids 'X' and 'Y' boil at $130^\circ\text{C}$ and $180^\circ\text{C}$ respectively. Which of the two liquids will have a higher vapour pressure at $90^\circ\text{C}$? Give a reason.
Answer
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From ISC 2025 Improvement Chemistry Paper 1, question 21(i).