R × (700 - T) .....(i) Heat obtained by upper compartment = 2 ×
7
2
R × (T - 400) ......(ii) By equating (i) and (ii) 5(700 - T) = 7(T - 400) 3000 - 5T = 7T- 2800 6300= 12T T = 525K ∴ Work done by lower gas = nR∆T = - 350 R Work done by upper gas = nR∆T = + 250 R Net work done = - 100 R