Question

The reaction between aluminum and iron (III) oxide is tremendously exothermic and produces enough heat to weld railway tracks together. The products of the reaction are iron and aluminum ox 2 3 ide (Al O ).

a. Write a balanced chemical equation for this reaction.

b. How much heat is liberated when 3.21 g of iron (III) oxide are reduced by aluminum at constant pressure (at 298.15 K)?

Answer 1

a) The balanced chemical equation for the reaction is

2 Al(s) + Fe₂O₃(s) 2Fe(s) + Al₂O₃(s)

b) The enthalpy of reaction for thermite reaction is H_rxn = -850 kJ [ Literature value]

From the balanced equation, we see that 1 mole of  Fe₂O₃(s) produces 850 kJ of energy on reduction by aluminium at constant pressure.

Molar mass of Fe₂O₃=159.69 g/mol

Therefore, 159.69 g  of  Fe₂O₃(s) produces 850 kJ of energy .

Energy produced by 3.21 g of Fe₂O₃(s)= ( -850 kJ / 159.69 g) x 3.21 g

=17.086 kJ