Entropy Change (Ideal Gas)

\Delta S = nC_V \ln\frac{T_f}{T_i} + nR\ln\frac{V_f}{V_i}

Entropy change for ideal gas between two states.

Variables

ΔS

Entropy change

Change in entropy

J/K

n

Moles

Amount of gas

mol

C_V

Molar heat capacity

At constant volume

J/(mol·K)

T_f

Final temperature

Final temp

K

T_i

Initial temperature

Initial temp

K

R

Gas constant

8.314

J/(mol·K)

V_f

Final volume

Final volume

m³

V_i

Initial volume

Initial volume

m³

Derivation

dS = dQ/T = (nC_V dT + PdV)/T, integrate.

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