Which of the following statements are true for the reaction of Fe₂O₃ with aluminium? 1. It is known as the ‘thermite reaction’. 2. The heat evolved is used for welding purpose. 3. Aluminium metal acts as an oxidizing agent. 4. Molten Fe and Al are formed at the end of the reaction. Select the correct answer using the code given below.
- (a)1 and 2
- (b)1 and 3
- (c)2 and 4
- (d)1 and 4
Correct — A, 1 and 2. The first two statements are textbook, the last two are wrong in ways worth pinning down. Iron(III) oxide and aluminium do react as NCERT writes it — Fe₂O₃(s) + 2Al(s) → 2Fe(l) + Al₂O₃(s) + Heat — and the chapter names it: 'the reaction of iron(III) oxide (Fe₂O₃) with aluminium is used to join railway tracks or cracked machine parts. This reaction is known as the thermit reaction.' So statement 1 stands, and statement 2 with it, since joining rail and cracked machine parts is welding and the heat is what does it. Statement 3 reverses the chemistry. Aluminium takes the oxygen away from the iron, so aluminium is oxidised and is therefore the reducing agent; Fe₂O₃, which loses its oxygen, is the oxidising agent. Statement 4 gets the products half right. The heat released is enough to leave the iron molten — NCERT's equation marks it (l) — but the aluminium ends up combined as solid aluminium oxide, not as molten aluminium. Only the first two survive.
- (b)1 and 3 — Keeps the name of the reaction but pairs it with the claim that aluminium is the oxidising agent. Aluminium is the one taking on oxygen here, which makes it the reducing agent.
- (c)2 and 4 — The welding use is right, but the products are not molten iron and molten aluminium. The aluminium leaves the reaction as Al₂O₃, a solid oxide, having given up its metal state to strip the oxygen off the iron.
- (d)1 and 4 — The name is right, the products are not. Molten iron, yes — that is exactly what runs into the mould around the rail ends — but alongside it sits aluminium oxide as slag, not aluminium metal.
The thermit reaction is a displacement between a metal and another metal's oxide, driven by the fact that aluminium sits well above iron in the reactivity series and holds oxygen far more firmly. It is so exothermic that the iron produced comes out as a liquid, hot enough to be poured. The industrial use follows directly: a portable crucible of iron oxide and aluminium powder is set off over a mould clamped around two rail ends, the molten iron runs into the gap, and the joint cools into continuous track. Aluminium oxide, being lighter, floats off as slag.
Two of the four statements can be settled by remembering the equation and two by thinking about who gives oxygen to whom. Once you write Fe₂O₃ + 2Al → 2Fe + Al₂O₃, statement 4 answers itself, because the aluminium is plainly on the right-hand side as an oxide. Statement 3 is the classic redox reversal, and the phrase to hold on to is that the reducing agent is the substance that gets oxidised. Aluminium starts as a metal and ends in an oxide, so it is oxidised, so it reduces the iron. Candidates who go by the feeling that the more reactive metal must be doing the oxidising get this backwards every time. It is also worth noticing that the code offers no option containing three statements, so exactly two are meant to be true.
- NCERT Class 10 Science gives the reaction as Fe₂O₃(s) + 2Al(s) → 2Fe(l) + Al₂O₃(s) + Heat and calls it the thermit reaction.
- It is used to join railway tracks and cracked machine parts; the iron is produced molten because so much heat is released.
- Aluminium is oxidised and is the reducing agent; iron(III) oxide is reduced and is the oxidising agent.
- The reaction can reach around 2500 °C with iron(III) oxide.
- The first commercial application was the welding of tram tracks at Essen in 1899.
- Calling aluminium the oxidising agent because it is the more reactive metal. The reducing agent is the one that gets oxidised.
- Assuming both metals come out molten. Only the iron does; the aluminium leaves as its oxide.
- Confusing the thermit reaction with the thermal decomposition of an oxide, which is a different process altogether.
As a statements item on the products and use of the thermite reaction, or as a redox question asking which species is oxidised in Fe₂O₃ + Al.
No directly related past PYQ was found.
- practice — not a real PYQ
In the reaction Fe₂O₃ + 2Al → 2Fe + Al₂O₃, aluminium acts as
- (a)an oxidising agent
- (b)a reducing agent
- (c)a catalyst
- (d)a dehydrating agent
Answer(b) a reducing agent — aluminium takes the oxygen from iron(III) oxide and is itself oxidised, so it reduces the iron.
- practice — not a real PYQ
The thermite reaction is put to industrial use mainly for
- (a)electroplating of iron
- (b)joining railway tracks
- (c)galvanising steel sheets
- (d)purifying bauxite
Answer(b) joining railway tracks — the molten iron it produces is run into a mould around the rail ends to make a continuous joint.