A quantity of monatomic ideal gas expands adiabatically from a volume of 2.0 liters to 6.0 liters. If the initial pressure is P0, what is the final pressure?

Answer 1

In an expansion of this type,

P*V^g = constant

where g is the specific heat ratio Cp/Cv, which for a monatomic gas is 5/3. Let Pf be the final pressure. The final volume is Vf = 3 Vo. Thus

Po*Vo^5/3 = Pf*(3Vo)^5/3
Pf/Po = (1/3)^(5/3) = 0.160