Certain amount (say, n moles) of a monoatomic ideal gas (C_v= 3 2 R ) of volume V₁ , temperature T₁ , and pressure P₁ is expanded against a constant external pressure P ₂ until the pressure of the gas becomes P₂ . The correct statement is

Options

1. AIf the expansion is carried out adiabatically, the work done is given by w = 3 5 ~V ₁ ( P ₂- P ₁ )
2. BIf the expansion is carried out adiabatically, the entropy change is given by S =0 .
3. CIf the expansion is carried out isothermally, the work done is given by w =- nRT ₁ ( P₁ P₂ )
4. DIf the expansion is carried out isothermally, the entropy change is given by S =- nR ( P₁ P₂ ) .