Question

Calculate the enthalpy change for the thermite reaction: 2al(s)+fe2o3(s)→2fe(s)+al2o3(s), δh∘rxn=−850 kj when 12.0 mol of al undergoes the reaction with a stoichiometrically equivalent amount of fe2o3.

Answer 1

Answer : 5100 KJ

Explanation : In the given reaction of 

$Fe_{2} O_{3} + 2Al ----\ \textgreater \ Al_{2}O_{3} + 2Fe$

we can see that 2 moles of Al is producing -850 KJ of energy

so for 12 moles of Al we can calculate as;

12 moles of Al X$\frac{-850}{2 moles of Al}$ = -5100 KJ

So, we can say that 12 moles of Al will need -5100 KJ of energy.