A general thermodynamic process can be expressed as PV n = constant, where molar heat capacity is C = + and work done W = . A soap bubble of radius R containing one mole of an ideal monoatomic gas. The surface tension of soap solution in T. The bubble is now supplied heat such that the heat supplied is two times the increment of internal energy of the gas. As a result, the radius of the bubble becomes two times. After this, the bubble is connected with a narrow tube. The radius of the bubble starts decreasing such that the temperature of the gas remains constant. Atmospheric pressure is P 0 .

(i) The work done by the gas in doubling the radius is–