Calculate The Enthalpy of Carbon Dioxide in The Following Reaction

Introduction

The enthalpy of carbon dioxide formation (ΔH°f) is a fundamental thermodynamic property that measures the heat released or absorbed when one mole of CO₂ is formed from its constituent elements under standard conditions (25°C and 1 atm).

In chemical reactions, enthalpy changes are crucial for predicting reaction feasibility, energy requirements, and product stability. For the reaction:

We can calculate the enthalpy change using standard enthalpies of formation.

How to Calculate

To calculate the enthalpy of carbon dioxide formation, follow these steps:

1. Identify the standard enthalpies of formation (ΔH°f) for all reactants and products.
2. Apply Hess's Law: ΔH°rxn = ΣΔH°f(products) - ΣΔH°f(reactants).
3. For the reaction C(s) + O₂(g) → CO₂(g), use standard values:
   • ΔH°f(CO₂) = -393.5 kJ/mol
   • ΔH°f(C) = 0 kJ/mol (element in standard state)
   • ΔH°f(O₂) = 0 kJ/mol (element in standard state)
4. Calculate ΔH°rxn = ΔH°f(CO₂) - [ΔH°f(C) + ΔH°f(O₂)] = -393.5 kJ/mol.

The negative sign indicates an exothermic reaction, where heat is released to the surroundings.

Example Calculation

Let's calculate the enthalpy change for the formation of 2 moles of CO₂:

1. Standard enthalpy of formation for CO₂: -393.5 kJ/mol
2. For 2 moles: 2 × (-393.5 kJ/mol) = -787 kJ
3. This means 787 kJ of heat is released when 2 moles of CO₂ are formed.

Interpretation

The calculated enthalpy change provides several key insights:

• Energy Release: The negative value indicates the reaction releases energy (exothermic).
• Reaction Feasibility: The large magnitude suggests this is a highly energetic reaction.
• Thermodynamic Stability: The energy released contributes to the stability of CO₂ as a product.