Question

In an iron thermit, how many moles of aluminium reacts with three moles of iron oxide to give nine moles of iron?

(a) 6

(b) 7

(c) 8

(d) 9

The question was posed to me in an interview.

The question is from Thermit Welding in portion Welding and Related Processes of Casting-Forming-Welding II

Answer 1

The correct answer is:

(a) 6

In the thermite reaction, the balanced chemical equation is:

Fe2O3+2Al→2Fe+Al2O3Fe2​O3​+2Al→2Fe+Al2​O3​

This shows that 1 mole of iron(III) oxide (Fe₂O₃) reacts with 2 moles of aluminum (Al) to produce 2 moles of iron (Fe).

If 3 moles of iron(III) oxide (Fe₂O₃) are used, the amount of aluminum required is calculated as:

3 moles of Fe2O3×2 moles of Al1 mole of Fe2O3=6 moles of Al3moles of Fe2​O3​×1mole of Fe2​O3​2moles of Al​=6moles of Al

Thus, 6 moles of aluminum are needed to react with 3 moles of iron oxide.