Chemistry
Entropy Calculator
Work out an entropy change from reaction entropies, from an isothermal gas expansion, or from enthalpy and free energy.
Your inputs
Change any value to update the result instantly.
Entropy change ΔS
80 J/K
In kJ/K
0.08 kJ/K
Method used
Products minus reactants, using standard molar entropies
Direction
Entropy increases — the system becomes more disordered
TΔS at your temperature
23.852 kJ
Only the inputs for the selected mode are used. Standard entropies are absolute values in J/(mol·K), so multiply each by its coefficient before entering the totals.
What this calculator does
Calculates an entropy change from standard entropies, from an isothermal ideal-gas expansion, or from enthalpy and free energy.
What your result means
A positive value means the system becomes more disordered; a negative value means it becomes more ordered.
Formula and working
ΔS = ΣνS°(products) − ΣνS°(reactants); ΔS = nR·ln(V₂/V₁); ΔS = (ΔH − ΔG)/T
- 1
Collect the inputs
Calculation mode = 1; Σ S° products = 400 J/K; Σ S° reactants = 320 J/K; Moles of gas = 1 mol; Initial volume = 1 L; Final volume = 10 L; ΔH = 50 kJ; ΔG = -20 kJ; Temperature = 298.15 K
- 2
Apply the formula
ΔS = ΣνS°(products) − ΣνS°(reactants); ΔS = nR·ln(V₂/V₁); ΔS = (ΔH − ΔG)/T
- 3
Result
Entropy change ΔS = 80 J/K
Frequently asked questions
Symbols and assumptions
- ΔS
- Entropy change
- R
- Gas constant
- T
- Absolute temperature
- • Standard entropies are absolute values already multiplied by their coefficients.
- • The gas mode assumes ideal behaviour at constant temperature.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • Only the inputs belonging to the chosen mode are used.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
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