Question

(A) 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

(a) Cooking is faster in a pressure cooker than in an open pan: Cooking is faster in a pressure cooker because the pressure inside the cooker is higher than atmospheric pressure. This leads to an increase in the boiling point of water. As a result, the water in the cooker can reach a higher temperature before it boils, which speeds up the cooking process. In an open pan, the water boils at a lower temperature, so the food takes longer to cook. 

(b) On mixing liquid X and liquid Y, volume of the resulting solution decreases: When mixing two liquids and the volume decreases, it indicates that there is an interaction between the molecules of liquid X and Y that causes them to pack more closely together, resulting in a decrease in the overall volume. This type of behavior shows a negative deviation from Raoult's law, which occurs when the intermolecular forces between the components of the mixture are stronger than the forces in the pure components. 

(C) Change in temperature after mixing liquids X and Y: When a negative deviation occurs, the mixing of the liquids is usually exothermic, meaning it releases heat. As a result, the temperature of the solution would increase. This happens because the interaction between the molecules in the mixture is stronger than in the individual pure liquids, and energy is released when these interactions are formed. \vspace{10pt}