How to Calculate Thermochem
What is Thermochem?
Thermochemistry measures heat involved in reactions: ΔH (enthalpy change), ΔS (entropy change), ΔG (Gibbs free energy).
Step-by-Step Guide
- 1Input reaction and temperature
- 2Calculate ΔH from bond energies or Hess's law
- 3Determine spontaneity: ΔG = ΔH - TΔS
Worked Examples
Input
Combustion: exothermic (ΔH < 0), entropy increases (ΔS > 0)
Result
Spontaneous at all temperatures (ΔG < 0)
Common Mistakes to Avoid
- ✕Assuming exothermic always spontaneous
- ✕Not accounting for temperature dependence
Frequently Asked Questions
When is reaction spontaneous?
ΔG < 0; depends on temperature through ΔH - TΔS balance.
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