1. What is the Enthalpy Change Formula?

The enthalpy change (ΔH) of a reaction is the difference between the sum of the standard enthalpies of formation of the products and the sum of the standard enthalpies of formation of the reactants. For NaCl, this represents the energy change when sodium and chlorine form sodium chloride.

2. How Does the Calculator Work?

The calculator uses the enthalpy change formula:

Where:

• \( \Delta H \) — Enthalpy change of reaction (kJ/mol)
• \( \Delta H_f(products) \) — Sum of formation enthalpies of products
• \( \Delta H_f(reactants) \) — Sum of formation enthalpies of reactants

Explanation: The equation calculates the net energy change by comparing the energy content of products versus reactants.

3. Importance of Enthalpy Calculation

Details: Calculating enthalpy change is crucial for understanding whether a reaction is exothermic (releases heat) or endothermic (absorbs heat), and for predicting reaction feasibility.

4. Using the Calculator

Tips: Enter the sum of formation enthalpies for products and reactants in kJ/mol. The calculator will compute the enthalpy change of the reaction.

5. Frequently Asked Questions (FAQ)

Q1: What is the standard enthalpy of formation for NaCl?
A: The standard enthalpy of formation for NaCl(s) is -411.12 kJ/mol at 298K.

Q2: How is this different from bond enthalpy?
A: Bond enthalpy considers energy to break/make specific bonds, while formation enthalpy considers energy to form compounds from elements in standard states.

Q3: What are typical values for NaCl formation?
A: The formation of NaCl from Na(s) and Cl₂(g) is highly exothermic, with ΔH°f = -411.12 kJ/mol.

Q4: Does temperature affect these calculations?
A: Standard enthalpies are typically given at 298K. Significant temperature changes may require heat capacity corrections.

Q5: Can this be used for solution enthalpies?
A: For solution enthalpies, you would need additional terms for the dissolution process and hydration energies.