Question
2 moles of a diatomic gas are enclosed in a vessel. when a certain amount of heat is supplied, 50% of the gas molecules get dissociated, bit there is no rise in temperature. What is the heat supplied if the temperature is T?
(1) RT
(2) RT/2
(3) 11RT/2
(4) 5RT
Joshi sir comment
internal energy of 2 mole diatomic gas = 2*5/2 RT = 5RT
now after 50% disociation in monoatomic form total internal energy
of 1 mole diatomic gas = 1*5/2 RT = 2.5 RT
and that of 2 mole monoatomic = 2*3/2 RT = 3RT ( 2 mole monoatomic gas will be formed by the dissociation of 1 mole diatomic gas)
so internal energy change = 1/2 RT
This internal energy increment will be equal to the heat provided