Calculate Delta H Rxn for The Following Reaction Fe2o3 3co

Introduction

The enthalpy change (ΔH) for a reaction is a measure of the heat absorbed or released during the reaction. For the reaction Fe2O3 + 3CO → Fe + 3CO2, we can calculate ΔH using standard enthalpies of formation (ΔHf°), which are the enthalpy changes when 1 mole of a compound is formed from its elements in their standard states.

Hess's Law allows us to calculate ΔH for any reaction by knowing the standard enthalpies of formation of all reactants and products. The formula is:

Where ΔHf°(products) is the sum of the standard enthalpies of formation of all products, and ΔHf°(reactants) is the sum of the standard enthalpies of formation of all reactants.

How to Calculate ΔH rxn

Step 1: Identify the Reaction

The reaction is Fe2O3 + 3CO → Fe + 3CO2. We need to know the standard enthalpies of formation for all four compounds involved.

Step 2: Find Standard Enthalpies of Formation

Standard enthalpies of formation are typically found in chemistry reference books or online databases. For this reaction, we'll use the following values (in kJ/mol):

• Fe2O3: -824.2 kJ/mol
• CO: -110.5 kJ/mol
• Fe: 0 kJ/mol (by definition)
• CO2: -393.5 kJ/mol

Step 3: Apply Hess's Law

Using the formula ΔH rxn = ΣΔHf°(products) - ΣΔHf°(reactants), we calculate:

Substituting the values:

The negative sign indicates that the reaction is exothermic, releasing 24.8 kJ of heat.

Example Calculation

Let's walk through an example calculation for the reaction Fe2O3 + 3CO → Fe + 3CO2.

Given Values

• ΔHf°(Fe2O3) = -824.2 kJ/mol
• ΔHf°(CO) = -110.5 kJ/mol
• ΔHf°(Fe) = 0 kJ/mol
• ΔHf°(CO2) = -393.5 kJ/mol

Calculation Steps

1. Calculate the sum of the enthalpies of formation of the products:
   ΔHf°(products) = ΔHf°(Fe) + 3ΔHf°(CO2) = 0 + 3(-393.5) = -1180.5 kJ
2. Calculate the sum of the enthalpies of formation of the reactants:
   ΔHf°(reactants) = ΔHf°(Fe2O3) + 3ΔHf°(CO) = -824.2 + 3(-110.5) = -824.2 - 331.5 = -1155.7 kJ
3. Apply Hess's Law to find ΔH rxn:
   ΔH rxn = ΔHf°(products) - ΔHf°(reactants) = -1180.5 - (-1155.7) = -1180.5 + 1155.7 = -24.8 kJ

Result Interpretation

The calculated ΔH rxn of -24.8 kJ indicates that the reaction releases 24.8 kJ of heat per mole of Fe2O3 reacted. This is an exothermic reaction.

Interpreting Results

When you calculate ΔH rxn for the reaction Fe2O3 + 3CO → Fe + 3CO2, the result tells you several important things:

• Exothermic or Endothermic: A negative ΔH indicates an exothermic reaction (heat is released), while a positive ΔH indicates an endothermic reaction (heat is absorbed).
• Energy Change: The magnitude of ΔH shows how much energy is involved in the reaction. Larger absolute values indicate more significant energy changes.
• Feasibility: Exothermic reactions are often more feasible in practical applications because they release energy that can be used.

For this specific reaction, the negative ΔH of -24.8 kJ means it's exothermic and releases 24.8 kJ of heat per mole of Fe2O3 reacted.