If the boundary of system moves by an infinitesimal amount, the work involved is given by `dw= -P_("ext") dV`, for irreversible process `W= -P_("ext") Delta V` (where `Delta V= V_(f) - V_(i)`). For reversible process. `P_("ext") = P_("int") +- dP ~= P_("int")`, so for reversible isothermal process `W = -nRT "In" (V_(f))/(V_(i))`
2 mole of an ideal gas undergoes isothermal compression along three different paths:
(i) reversible compression from `P_(i) = 2` bar and `V_(i) = 8L " to" P_(f) = 20` bar
(ii) a single stage compression against a constant external pressure of 20 bar
(iii) a two stage compression consisting initially of compression against a constant external pressure of 10 bar until `P_("gas") = P_("ext")`, followed by compression aganist a constant pressure of 20 bar until `P_("gas") = P_("ext")`
Work done (in bar -L) on the gas in reversible isothermal compression is:

Options

A. 9.212
B. 36.848
C. 18.424
D. None of these

Answer

B