Question

Give reasons:
(a) Cooking is faster in a pressure cooker than in an open pan.
(b) On mixing liquid X and liquid Y, volume of the resulting solution decreases. What type of deviation from Raoult's law is shown by the resulting solution? What change in temperature would you observe after mixing liquids X and Y?

Hint:

Negative deviation from Raoult's law occurs when the intermolecular forces between the components of the solution are stronger than in the pure state, leading to a decrease in volume and an exothermic mixing process.

Answer 1

1. Cooking Efficiency of Pressure Cookers:

Explanation:
Pressure cookers achieve higher internal pressure compared to open pans. This increased pressure elevates the boiling point of water. Consequently, food cooks at a higher temperature, accelerating the cooking duration. In open pans, water boils at 100°C, whereas in a pressure cooker, the boiling point exceeds 100°C, leading to faster cooking.

2. Volume Contraction Upon Mixing Liquids X and Y:

Deviation from Raoult's Law:
The solution exhibits negative deviation from Raoult's law. This occurs because the intermolecular forces between X and Y molecules are stronger than the forces within the individual liquids. This results in a combined volume smaller than the sum of the initial volumes of X and Y.

Temperature Change:
Mixing liquids with strong intermolecular attractions releases energy due to new bond formation between X and Y molecules. This energy release characterizes an exothermic reaction. Therefore, the temperature of the mixture increases upon combining the liquids.