Q liberado (m·ΔH)
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The Q released (m·ΔH) calculator computes the heat released or absorbed in a chemical reaction, using the mass of the substance and the enthalpy change (ΔH). The formula Q = m·ΔH/M connects mass (m), molar mass (M) in g/mol, and enthalpy change (ΔH) in kJ/mol. It's used in thermodynamics to predict energy flow in industrial, laboratory, or academic processes.
To use the formula, input the substance's mass in grams, its molar mass, and the ΔH of the reaction. The mass divided by molar mass converts grams to moles, then multiplied by ΔH. Units matter: if ΔH is given in kJ/g instead of kJ/mol, skip dividing by molar mass.
This calculator is applied in scenarios like predicting heat from chemical fires, calculating fuel efficiency, or estimating energy needs for reactions. In labs, it helps adjust proportions for accurate results.
Common precautions include verifying ΔH is correct for reaction conditions (standard pressure/temperature), ensuring mass is in grams, and confirming molar mass calculations. Unit conversion errors can invalidate outcomes.
Frequently asked questions
What is the difference between mass and moles in the formula?
Mass is the substance quantity in grams. Moles are calculated by dividing mass by molar mass. The formula converts grams to moles to apply ΔH per mole.
Can I use the calculator with negative ΔH?
Yes. Negative ΔH indicates an exothermic reaction (heat release). The Q result will have the same sign, showing energy released.
Do I need to convert mass units for the formula?
Yes. The formula requires mass in grams. If mass is in kilograms, convert by multiplying by 1000.
Why is molar mass important in the calculation?
Molar mass converts the substance's mass into moles, which is the unit needed to multiply by the enthalpy change (ΔH).
Does the calculator work for reactions with multiple substances?
Not directly. For reactions with multiple substances, calculate Q separately for each component and sum the results.