calculate the delta H for
3 Fe(s) + 4 CO2(g) �¨ 4 CO(g) + Fe3O4(s)
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dHrxn = (n*dHf products) - (n*dHf reactants)
To calculate the enthalpy change (ΔH) for a reaction, you need to know the individual enthalpies of formation (∆Hf) of the reactants and products involved in the reaction. The ∆Hf values represent the change in enthalpy when one mole of a compound is formed from its constituent elements in their standard states at a given temperature.
Here are the steps to calculate ΔH for the given reaction:
Step 1: Write the balanced chemical equation for the reaction.
3 Fe(s) + 4 CO2(g) → 4 CO(g) + Fe3O4(s)
Step 2: Identify the enthalpies of formation (∆Hf) for all the reactants and products involved in the reaction. You can find these values in a reference table or database. For this reaction, you will need the ∆Hf values for Fe(s), CO2(g), CO(g), and Fe3O4(s).
∆Hf(Fe(s)) = 0 kJ/mol (standard state)
∆Hf(CO2(g)) = -393.5 kJ/mol
∆Hf(CO(g)) = -110.5 kJ/mol
∆Hf(Fe3O4(s)) = -1118 kJ/mol
Step 3: Determine the stoichiometric coefficients for the reactants and products in the balanced equation and use them to set up a thermochemical equation.
ΔH = (Σ n × ∆Hf(products)) - (Σ n × ∆Hf(reactants))
ΔH = (4 mol CO × ∆Hf(CO(g))) + (1 mol Fe3O4 × ∆Hf(Fe3O4(s))) - (3 mol Fe × ∆Hf(Fe(s))) - (4 mol CO2 × ∆Hf(CO2(g)))
Step 4: Substitute the known values into the equation and perform the calculation to find the ΔH of the reaction.
ΔH = (4 mol CO × -110.5 kJ/mol) + (1 mol Fe3O4 × -1118 kJ/mol) - (3 mol Fe × 0 kJ/mol) - (4 mol CO2 × -393.5 kJ/mol)
ΔH = -442 kJ/mol + (-1118 kJ/mol) + 0 kJ/mol + 1574 kJ/mol
ΔH = -442 kJ/mol - 1118 kJ/mol + 1574 kJ/mol
ΔH = 14 kJ/mol
Therefore, the ΔH for the given reaction is 14 kJ/mol.