# Enthalpy / Heat of Reaction Calculator

Free enthalpy calculator. Calculate heat (q = mcΔT), enthalpy change (ΔH), and determine if a reaction is exothermic or endothermic.

## What this calculates

Calculate heat transfer using q = mcΔT and determine enthalpy changes for chemical reactions. Find heat (q), mass, temperature change, or specific heat capacity.

## Inputs

- **Solve For** — options: Heat (q), Mass (m), Temperature Change (ΔT), Specific Heat (c) — Select what to calculate.
- **Mass** (g) — min 0 — Mass of the substance in grams.
- **Specific Heat Capacity** (J/(g·°C)) — min 0 — Specific heat capacity. Water = 4.184 J/(g·°C).
- **Initial Temperature** (°C) — Temperature before the reaction.
- **Final Temperature** (°C) — Temperature after the reaction.
- **Heat (q)** (J) — Heat absorbed or released in joules.
- **Moles of Reactant (optional)** (mol) — min 0 — Enter moles to calculate ΔH in kJ/mol.

## Outputs

- **Result** — The calculated value.
- **Unit** — formatted as text — Unit of the result.
- **Heat (kJ)** (kJ) — Heat in kilojoules.
- **ΔH per mole** (kJ/mol) — formatted as text — Enthalpy change per mole of reactant.
- **Reaction Type** — formatted as text — Whether the reaction is exothermic or endothermic.
- **Formula** — formatted as text — Calculation steps.

## Frequently Asked Questions

**Q: What is enthalpy?**

A: Enthalpy (H) is the total heat content of a system. Enthalpy change (ΔH) measures heat absorbed or released during a reaction at constant pressure. Negative ΔH means exothermic (releases heat); positive means endothermic (absorbs heat).

**Q: What is the formula q = mcΔT?**

A: q = mcΔT relates heat (q) to mass (m), specific heat capacity (c), and temperature change (ΔT = T_final - T_initial). It is used in calorimetry to measure heat changes in reactions.

**Q: What is the specific heat of water?**

A: The specific heat of liquid water is 4.184 J/(g·°C). This is relatively high, which is why water is commonly used as a calorimeter solvent and why it takes a lot of energy to heat water.

**Q: How do I convert q to ΔH?**

A: ΔH (per mole) = q / moles of reactant. Make sure to convert joules to kilojoules (divide by 1000) since ΔH is typically reported in kJ/mol. The sign indicates direction: negative for exothermic, positive for endothermic.

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Source: https://vastcalc.com/calculators/chemistry/enthalpy
Category: Chemistry
Last updated: 2026-04-21