Question

The thermite reaction used for welding of metals involves the reaction

2Al(s) + Fe₂O₃(s) → Al₂O₃(s) + 2Fe(s)

What is Δr, H° at 25°C for this reaction

Given that the standard heats of format in of Al₂O₃ and Fe₂O₃ are –1675.7 kJ and –828.4 kJmol^-1respectively.

Answer 1

2AL(s) + fe₂O₃₍s) \(\longrightarrow\) AL₂O₃(s) + 2fe(s)

Δ_fH_(AL2O3) = - 1675.7 KJ/mol and Δ_fH_fe2O3 = - 828.4 KJ/mol

Δ_rH = Δ_fH product - Δ_fH reactant 

= (Δ_fH_(AL2O3) + Δ_fH_fe(s)) - (Δ_fH_AL(s) + Δ_fH_(fe2O3))

= (-1675.7 KJ/mol + 0) - 0 + (-828.4 KJ/mol)

Δ_rH = -847.3 KJ/mol