Final answer:
The enthalpy change (ΔH) when 235 g of Fe₂O₃ reacts completely is −39.4 kJ, calculated using the molar mass of Fe₂O₃ and the given ΔH° from the thermochemical equation.
option c is the correct
Step-by-step explanation:
The question asks for the value of ΔH when 235 g of iron(III) oxide reacts completely using the given thermochemical equation: Fe₂O₃(s) + 3CO(g) → 2Fe(s) + 3CO₂(g) ΔH° = −26.8 kJ. To find the value of ΔH for 235 g of Fe₂O₃, we need to first calculate the number of moles of Fe₂O₃ that 235 g corresponds to and then use the given ΔH for the mole-based reaction to determine the enthalpy change for the actual amount of Fe₂O₃.
The molar mass of Fe₂O₃ is calculated as (2 × 55.85 g/mol for Fe) + (3 × 16.00 g/mol for O) = 159.7 g/mol. We can determine the number of moles in 235 g of Fe₂O₃ as follows:
Number of moles = mass (g) / molar mass (g/mol) = 235 g / 159.7 g/mol = 1.471 moles of Fe₂O₃.
Since the given ΔH° is for 1 mole of Fe₂O₃, we can calculate the ΔH for 1.471 moles:
ΔH for 1.471 moles = ΔH° × number of moles = −26.8 kJ × 1.471 = −39.4 kJ.
Therefore, the value of ΔH when 235 g of Fe₂O₃ reacts completely is −39.4 kJ, which corresponds to answer choice (c).