Thermochemistry Calculator

Calculate heat transfer, enthalpy changes, solve calorimetry problems, and apply Hess's Law.

Calorimetry Calculator (q = mcΔT)

Calculate heat transfer using the calorimetry equation.

J/(g·°C)
Water: 4.184 J/(g·°C), Aluminum: 0.897, Iron: 0.449
°C
°C
Example Problems:
⭐ Water Heating
100g water, 25°C → 75°C 250g water, 20°C → 100°C (boiling) Heat 500g water with 10.46 kJ
⭐⭐ Metal Heating
50g aluminum, 20°C → 150°C Find c: 100g metal, ΔT=60°C, q=2688J 75g iron cooling, 100°C → 25°C
⭐⭐⭐ Coffee Cup Calorimetry
200g water, 22°C → 28.5°C (reaction)
Enthalpy Change Calculator

Calculate enthalpy changes for reactions and processes.

Example Problems:
⭐ Exothermic Reactions
CH₄ combustion: 890 kJ/mol H₂ + ½O₂: 285.8 kJ (2 mol H₂O) HCl neutralization
⭐⭐ Endothermic Reactions
N₂ + O₂ → 2NO: 178 kJ NH₄NO₃ dissolution CO₂ decomposition
Hess's Law Calculator

Calculate ΔH for a target reaction using known reactions.

Known Reactions
Example Problems:
⭐ Carbon Monoxide Formation
C + ½O₂ → CO (from C + O₂ and CO + ½O₂)
⭐⭐ Methane Formation
C + 2H₂ → CH₄ (multi-step)
Phase Change Energy Calculator

Calculate energy for melting, freezing, vaporization, or condensation.

kJ/mol
g/mol
Example Problems:
⭐ Water Phase Changes
Melt 100g ice Melt 500g ice Boil 250g water Vaporize 2 mol water Sublimate 50g ice
⭐⭐ Organic Solvents
Boil 100g ethanol Melt 1 mol ethanol Boil 50g methanol Boil 75g acetone Vaporize 2 mol benzene
⭐⭐ Gases
Melt 1 mol ammonia Boil 32g oxygen Vaporize 2 mol nitrogen Melt 1 mol hydrogen
⭐⭐⭐ Metals
Melt 200g mercury Boil 100g mercury Melt 1 mol sodium Melt 100g aluminum Melt 1 mol iron
⭐⭐⭐⭐ Sublimation
Sublimate 100g dry ice (CO₂) Sublimate 1 mol ice
Results


Enter data and click Calculate to see results

Understanding Thermochemistry
Key Concepts
  • Heat (q): Energy transferred between systems
  • Enthalpy (ΔH): Heat change at constant pressure
  • Exothermic: Releases heat (ΔH < 0)
  • Endothermic: Absorbs heat (ΔH > 0)
  • Specific Heat (c): Heat per gram per degree
Important Equations
  • q = mcΔT - Calorimetry equation
  • ΔH°rxn = Σ ΔH°f(products) - Σ ΔH°f(reactants)
  • q = n × ΔH - Heat from moles
  • ΔHsub = ΔHfus + ΔHvap
Hess's Law

The total enthalpy change for a reaction is independent of the pathway taken.

Steps:

  1. Reverse reactions: change sign of ΔH
  2. Multiply reactions: multiply ΔH by factor
  3. Add reactions: add ΔH values
Common Values

Specific Heat (c):

  • Water: 4.184 J/(g·°C)
  • Ice: 2.09 J/(g·°C)
  • Aluminum: 0.897 J/(g·°C)
  • Iron: 0.449 J/(g·°C)

Water Phase Changes:

  • ΔHfus: 6.01 kJ/mol
  • ΔHvap: 40.7 kJ/mol

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