How to Calculate Enthalpy Change (Q=mcΔT)
What is Enthalpy Change (Q=mcΔT)?
Enthalpy (H) is a thermodynamic property measuring the total heat content of a system at constant pressure. Enthalpy change ΔH = q = m × c × ΔT for calorimetry calculations. Exothermic reactions release heat (ΔH < 0); endothermic absorb heat (ΔH > 0).
Step-by-Step Guide
- 1q = m × c × ΔT
- 2m = mass in grams
- 3c = specific heat capacity (water: 4.18 J/g·°C)
- 4ΔT = final temperature − initial temperature
- 5For combustion: q = −m_fuel × ΔHcombustion / molar mass
Worked Examples
Input
500g water heated from 20°C to 80°C
Result
q = 500×4.18×60 = 125,400 J = 125.4 kJ
Heat absorbed by water
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