Thermodynamics
Entropy Change (Ideal Gas)
Entropy change for ideal gas between two states.
Variables
ΔSJ/K
Entropy change
Change in entropy
nmol
Moles
Amount of gas
C_VJ/(mol·K)
Molar heat capacity
At constant volume
T_fK
Final temperature
Final temp
T_iK
Initial temperature
Initial temp
RJ/(mol·K)
Gas constant
8.314
V_fm³
Final volume
Final volume
V_im³
Initial volume
Initial volume
Derivation
dS = dQ/T = (nC_V dT + PdV)/T, integrate.
Your notes
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Common questions
What is the Entropy Change (Ideal Gas) formula?
Entropy Change (Ideal Gas) is written ΔS = nCᵥ lnT_f/Tᵢ + nRlnV_f/Vᵢ. Entropy change for ideal gas between two states. It belongs to Thermodynamics, under Entropy.
What are the units in ΔS = nCᵥ lnT_f/Tᵢ + nRlnV_f/Vᵢ?
In SI units, ΔS is entropy change, measured in kg·m²/(s²·K); n is moles, measured in mol; C_V is molar heat capacity, measured in kg·m²/(s²·mol·K); T_f is final temperature, measured in K; T_i is initial temperature, measured in K; R is gas constant, measured in kg·m²/(s²·mol·K); V_f is final volume, measured in m³; V_i is initial volume, measured in m³.
How is the Entropy Change (Ideal Gas) formula derived?
dS = dQ/T = (nC_V dT + PdV)/T, integrate. The result is ΔS = nCᵥ lnT_f/Tᵢ + nRlnV_f/Vᵢ.