If the pressure at station Q is 50 kPa, the change in entropy

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Direction: In an experimental set-up, air flows between two stations P and Q adiabatically. The direction of flow depends on the pressure and temperature conditions maintained at P and Q. The conditions at station P are 150 kPa and 350 K. The temperature at station Q is 300 K. The following are the properties and relations pertaining to air:
Specific heat at constant pressure, c_p = 1.005 kJ/kgK;
Specific heat at constant volume, c_v = 0.718 kJ/kgK;
Characteristic gas constant, R = 0.287 kJ/kgK.
Enthalpy, h = c_pT. .
Internal energy, u = c_vT.

If the pressure at station Q is 50 kPa, the change in entropy (s_Q – s_p) in kJ/kgK is

1. – 0.155
2. 0
3. 0.160
4. 0.355

Correct Option: C

∆s =	δq	for reversible process
	T

δQ = δW = P₁V₁ln	V₂
	V₁

∆s =		δq	= mRln	P₁
		T		p₂

∆s = mR ln	P₁
	P₂