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 is faster in a pressure cooker than in an open pan:

Reason:
In a pressure cooker, the pressure is higher than in an open pan. As a result, the boiling point of water increases. This higher boiling point allows the food to cook at a higher temperature, which speeds up the cooking process. In an open pan, the boiling point of water is at 100°C, while in a pressure cooker, the boiling point can rise above 100°C, making the cooking process faster.

2. On mixing liquid X and liquid Y, volume of the resulting solution decreases:

Deviation from Raoult's Law:
The resulting solution exhibits a negative deviation from Raoult's law. In this case, the intermolecular forces between the molecules of liquid X and liquid Y are stronger than the forces in the individual liquids. As a result, the total volume of the solution is less than the sum of the individual volumes of liquid X and liquid Y.

Change in Temperature:
When liquids with strong intermolecular attractions are mixed, energy is released due to the formation of new bonds between the molecules of X and Y. This release of energy typically leads to an exothermic reaction. Therefore, after mixing, the temperature of the solution will increase.