Dear sachin,

ΔH for a reaction is equal to the sum of the heats of formation of the product compounds minus the sum of the heats of formation of the reactant compounds:

ΔH = Σ ΔH_f products - Σ ΔH_f reactants

Omitting terms for the elements, the equation becomes:

ΔH = 4 ΔH_f Al₂O₃(s) - 3 ΔH_f Fe₃O₄(s)

The values for ΔH_f may be found in the Heats of Formation of Compounds table. Plugging in these numbers:

ΔH = 4(-1669.8 kJ) - 3(-1120.9 kJ)

ΔH = -3316.5 kJ

Please feel free to ask your queries here. We are all IITians and here to help you in your IIT JEE preparation.

All the best.

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Askiitians Expert

Sagar Singh

B.Tech, IIT Delhi

ΔH for a reaction is the sum of the heats of formation of the product compounds - the sum of the heats of formation of the reactant compounds:

ΔH = Σ ΔH_f products - Σ ΔH_f reactants

ΔH = 4 ΔH_f Al₂O₃(s) - 3 ΔH_f Fe₃O₄(s)

The values for ΔH_f are present in the Heats of Formation of Compounds table.

 ΔH = 4(-1669.8 kJ) - 3(-1120.9 kJ)

ΔH = -3316.5 kJ

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