An ideal gas of mass m and temperature T1 undergoes a reversible

An ideal gas of mass m and temperature T₁ undergoes a reversible isothermal process from an initial pressure P₁ to final pressure P₂. The heat loss during the process is Q. The entropy change ∆S of the gas is

For clausius theorem, ∮	δQ	< 0 (for irreversible Heat engine).
	T

mRln			P₂
			P₁

mRln			P₁
			P₂

mRln		P₂		-	Q
		P₁			T₁