Project ForgeThermodynamics
Entropy & Second Law
GATE 2018
Medium
An ideal gas undergoes a process from state 1 (T1=300 K, p1=100 kPa) to state 2 (T2=600 K, p2=500 kPa). The specific heats of the ideal gas are: cp=1 kJ/kg-K and cv=0.7 kJ/kg-K. The change in specific entropy of the ideal gas from state 1 to state 2 (in kJ/kg-K) is __________ (correct to two decimal places).
0.21 kJ/kg-K(± 0.01 accepted)
Explanation
R = cp−cv = 0.3 kJ/kg-K. Δs = cp·ln(T2/T1) − R·ln(p2/p1) = 1×ln(2) − 0.3×ln(5) = 0.6931 − 0.4828 ≈ 0.21 kJ/kg-K.
Source: GATE ME 2018 Session 1 (Set 1) (2018)
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