Two bodies of differet metals A and B having an equal mass are given equal quantities of heat. Given that the molecular weight of A is greater than that of B, compare the specific heat capacities of the two metals. (Note that the rise in temperature is a measure of the increase in the average kinetic energy of the molecules.).

Explanation

Specific heat capacity is the amount of heat energy absorbed by a unit mass of substance when its temperature is increased through 1K. Let A and B be two substances of unit masses. Let the molecular weight of A be greater than the molecular weight of `B(M_(A)gtM_(B))`. As the mass of A and B are equal, the number of molecules of B is greater than the number of molecules of `A(n_(B)gtn_(A))`.
When equal amount of heat energy is supplied to A and B, the kinetic energy per molecule of A is greater than that of B as the number of molecules of A is less than that of .B..
That is the rise in temperature of A is greater than the rise in temperature of B. Therefore, B can absorb more amount of heat energy at less temperature. So, the specific heat capacity decreases as the molecular weight increases.