WEBTi = 310K, Pi = 6.00 bar. 2.50 moles of an ideal gas with C v,m =3R/2 under goes a reversible adiabatic expansion until the final pressure is 1/4 th its initial value. T i = 310K, P i = 6.00 bar. What if the expansion was against a constant external pressure of 1.50 bar until the final pressure is 1/4 th its initial value.