Question

The formation of Fe₂O₃ from iron and oxygen at 298 K is depicted below.

2Fe(s) + 3/2 O₂ (g) → Fe₂O₃(s) triangleH rxn= -824.2 kJ mol⁻¹
Assuming the heat capacities do not change with temperature, what would the reaction enthalpy be at 657 K? CP.m is the constant-pressure molar heat capacity for a compound.
Fe=25.10 J k⁻¹ mol⁻¹
O₂= 29.36 J k⁻¹ mol⁻¹
Fe₂O₃ = 103.85 J k⁻¹ mol⁻¹

Answer 1

The enthalpy change of a reaction can be determined using Hess's law, which states that the total enthalpy change of a reaction is equal to the sum of the enthalpy changes of its individual steps.

Step-by-step explanation:

The enthalpy change of a reaction can be determined using Hess's law, which states that the total enthalpy change of a reaction is equal to the sum of the enthalpy changes of its individual steps. In this case, we can determine the enthalpy change at 657 K by considering the individual enthalpy changes of the formation of Fe₂O₃ at different temperatures.

Using the given heat capacities, we can calculate the enthalpy change at 657 K as follows:

1. Calculate the enthalpy change at 298 K using the given value (-824.2 kJ/mol).
2. Calculate the enthalpy change at 657 K for the formation of Fe₂O₃ using the heat capacities of Fe, O₂, and Fe₂O₃.
3. Subtract the enthalpy change at 298 K from the enthalpy change at 657 K to find the difference.

The resulting enthalpy change at 657 K can then be used to determine the energy flow of the reaction at that temperature.