A calorimeter of water equivalent 20 g contains 180 g of water at 25^oC. ‘m’ grams of steam at 100^oC is mixed in it till the temperature of the mixure is 31^oC. The value of ‘m’ is close to :
(Latent heat of water = 540 cal g^–1, specific heat of water = 1 cal g^{–1 o}C^–1)

A balloon filled with helium (32^oC and 1.7 atm.) bursts. Immediately afterwards the expansion of helium can be considered as

Consider a gas of triatomic molecules. The molecules are assumed to be triangular and made of massless rigid rods whose vertices are occupied by atoms. The internal energy of a mole of the gas at temperature T is :

An ideal gas in a closed container is slowly heated. As its temperature increases, which of the following statements are true?
(A) the mean free path of the molecules decreases.
(B) the mean collision time between the molecules decreases.
(C) the mean free path remains unchanged.
(D) the mean collision time remains unchanged.