Calculate Delta H Rxn for The Following Reaction Cao+co2

What is ΔH rxn?

The enthalpy change of reaction (ΔH rxn) measures the heat absorbed or released during a chemical reaction at constant pressure. It's a fundamental concept in thermodynamics that helps predict whether a reaction will be exothermic (releases heat) or endothermic (absorbs heat).

For the reaction CaO + CO₂, ΔH rxn represents the energy change when calcium oxide reacts with carbon dioxide. This reaction is particularly important in industrial processes like cement production and carbon capture technologies.

How to calculate ΔH rxn

The standard enthalpy change of reaction (ΔH° rxn) can be calculated using the standard enthalpies of formation (ΔH° f) of the products and reactants:

For the reaction CaO + CO₂, you would:

1. Find the standard enthalpy of formation for calcium carbonate (CaCO₃)
2. Find the standard enthalpies of formation for calcium oxide (CaO) and carbon dioxide (CO₂)
3. Apply the formula above

Note that standard enthalpies of formation are typically measured in kilojoules per mole (kJ/mol) at standard conditions (25°C and 1 atm pressure).

Example calculation

Let's calculate ΔH rxn for the reaction CaO + CO₂ → CaCO₃ using standard enthalpies of formation:

• ΔH° f (CaCO₃) = -1206.9 kJ/mol
• ΔH° f (CaO) = -635.1 kJ/mol
• ΔH° f (CO₂) = -393.5 kJ/mol

This result indicates the reaction releases 178.3 kJ of energy per mole of calcium carbonate formed, making it an exothermic process.

Interpretation of results

Interpreting ΔH rxn values requires understanding their sign and magnitude:

• Negative ΔH rxn: The reaction is exothermic (releases heat to the surroundings)
• Positive ΔH rxn: The reaction is endothermic (absorbs heat from the surroundings)
• Magnitude: Larger absolute values indicate more energy is involved in the reaction

For the CaO + CO₂ reaction, the negative ΔH rxn value confirms it's an exothermic process, which is important for understanding its energy efficiency in industrial applications.