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Vapour pressure plays an important role in calculating boiling point and the freezing point of…
Vapour pressure plays an important role in calculating boiling point and the freezing point of solutions. In cold countries salt is sprinkled on the road whereas while boiling egg, salt is added in water. Both these processes help the cause.
(a)[1.0]
Explain relative lowering of vapour pressure.
(b)[1.0]
How adding salt to water help in boiling of egg?
(c)[1.0]
Why is salt sprinkled on road during winters?
Answer
Answer (a)
Official answer keyPure solvent has a certain vapour pressure. When a non-volatile solute is added into pure solvent, less solvent evaporates and hence, vapour pressure decreases. The ratio between the Vapour Pressure (V.P) difference to V.P. of pure solvent is known as relative lowering of V.P.
Answer (b)
Official answer keyAddition of salt increases the boiling point of aqueous solution and eggs get more heat for cooking.
Answer (c)
Official answer keyIt lowers the freezing point of ice.
From ISC 2025 Practice Chemistry, question 92.