Question

How many kilojoules of heat will be released when exactly 1 mole of iron, Fe, is burned to form Fe2O3 at standard state condaition?

Answer 1

Answer:

412.1kJ

Explanation:

For the reaction , from the question -

4Fe (s)  +  3O₂ (g)  → 2Fe₂O₃ (s)

Δ Hrxn = Δ H°f (products) - Δ H°f (reactants)

In case the compound is in its standard state , enthalphy of formation is zero

Hence ,

for the above reaction ,

ΔHrxn =( 2 * Δ H° (Fe₂O₃ )) - [ ( 4 *Δ H° Fe ) + (3 * Δ H° O₂ )]

The value for Δ H°(Fe₂O₃ ) = - 824.2kJ/mol

Δ H° Fe = 0

Δ H° O₂ = 0

Putting in the above equation ,

ΔH rxn = ( 2 * Δ H° (Fe₂O₃ ))  - 0

ΔHrxn =  2× - 824.2 kJ / mol = - 1648.4 kJ/mol

- 1648.4 kJ/mol  , this much heat is released by the buring of 4 mol of Fe.

Hence ,

for 1 mol of Fe ,

- 1648.4 kJ/mol  / 4 = 412.1kJ