1. What is Enthalpy Change?

Enthalpy change (ΔH) is the heat energy change in a chemical reaction at constant pressure. It indicates whether a reaction is exothermic (releases heat) or endothermic (absorbs heat).

2. How Does the Calculator Work?

The calculator uses the enthalpy change equation:

Where:

• \( \Delta H \) — Enthalpy change (kJ/mol)
• \( \Sigma \text{Products} \) — Sum of enthalpies of formation of products
• \( \Sigma \text{Reactants} \) — Sum of enthalpies of formation of reactants

Explanation: The equation calculates the difference between the total enthalpy of products and reactants in a chemical reaction.

3. Importance of ΔH Calculation

Details: Calculating enthalpy change is essential for understanding reaction thermodynamics, predicting reaction feasibility, and designing chemical processes.

4. Using the Calculator

Tips: Enter the sum of product enthalpies and sum of reactant enthalpies in kJ/mol. The calculator will compute the enthalpy change (ΔH).

5. Frequently Asked Questions (FAQ)

Q1: What does a negative ΔH value mean?
A: A negative ΔH indicates an exothermic reaction (heat is released to the surroundings).

Q2: What does a positive ΔH value mean?
A: A positive ΔH indicates an endothermic reaction (heat is absorbed from the surroundings).

Q3: What are standard enthalpy conditions?
A: Standard conditions are 298K (25°C) and 1 atm pressure, denoted as ΔH°.

Q4: How is this different from Gibbs free energy?
A: Gibbs free energy (ΔG) also considers entropy change and determines reaction spontaneity, while ΔH only considers heat change.

Q5: Can this be used for phase changes?
A: Yes, enthalpy change calculations apply to phase changes (e.g., heat of fusion, heat of vaporization).