(A) One mole of neon gas, initially at 300 K and 1.00 bar, expands adiabatically (i.e., with no heat lost to the surroundings) against a constant external pressure of 0.50 bar until the gas pressure is also 0.50 bar. The final temperature of the gas is 240 K. What is ΔS for the gas? The molar heat capacity of Ne(g) is 20.8 J mol^-1 K^-1.

(B) One mole of neon gas, initially at 300 K and 1.00 bar, expands isothermally against a constant external pressure of 0.50 bar until the gas pressure is also 0.50 bar. What is ΔS for the gas?