Justify that the following reactions are redox reactions-a CuO s - H 2 g - Cu s - H 2 O g b Fe 2 O 3 s -3 CO g - 2 Fe s -3 CO 2 g c 4 BCl 3 g -3 LiAlH 4 s - 2 B 2 H 6 g -3 LiCl s -3 AlCl 3 s d 2 K s - F 2 g - 2 K - F - s e 4 NH 3 g -5 O 2 g - 4 NO g -6 H 2 O g

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Types of Redox Reactions

Justify that ...

Question

Justify that the following reactions are redox reactions:

(a) CuO(s) + H₂(g) → Cu(s) + H₂O(g)

(b) Fe₂O₃(s) + 3CO(g) → 2Fe(s) + 3CO₂(g)

(c) 4BCl₃(g) + 3LiAlH₄(s) → 2B₂H₆(g) + 3LiCl(s) + 3 AlCl₃ (s)

(d) 2K(s) + F₂(g) → 2K+F– (s)

(e) 4 NH₃(g) + 5 O₂(g) → 4NO(g) + 6H₂O(g)

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Solution

(a)

Let us write the oxidation number of each element involved in the given reaction as:

Here, the oxidation number of Cu decreases from +2 in CuO to 0 in Cu i.e., CuO is reduced to Cu. Also, the oxidation number of H increases from 0 in H₂ to +1 in H₂O i.e., H₂ is oxidized to H₂O. Hence, this reaction is a redox reaction.

(b)

Let us write the oxidation number of each element in the given reaction as:

Here, the oxidation number of Fe decreases from +3 in Fe₂O₃ to 0 in Fe i.e., Fe₂O₃ is reduced to Fe. On the other hand, the oxidation number of C increases from +2 in CO to +4 in CO₂ i.e., CO is oxidized to CO₂. Hence, the given reaction is a redox reaction.

(c)

The oxidation number of each element in the given reaction can be represented as:

In this reaction, the oxidation number of B decreases from +3 in BCl₃ to –3 in B₂H₆. i.e., BCl₃ is reduced to B₂H₆. Also, the oxidation number of H increases from –1 in LiAlH₄ to +1 in B₂H₆ i.e., LiAlH₄ is oxidized to B₂H₆. Hence, the given reaction is a redox reaction.

(d)

The oxidation number of each element in the given reaction can be represented as:

In this reaction, the oxidation number of K increases from 0 in K to +1 in KF i.e., K is oxidized to KF. On the other hand, the oxidation number of F decreases from 0 in F₂ to –1 in KF i.e., F₂ is reduced to KF.

Hence, the above reaction is a redox reaction.

(e)

The oxidation number of each element in the given reaction can be represented as:

Here, the oxidation number of N increases from –3 in NH₃ to +2 in NO. On the other hand, the oxidation number of O₂ decreases from 0 in O₂ to –2 in NO and H₂O i.e., O₂ is reduced. Hence, the given reaction is a redox reaction.

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Similar questions

Q. Justify that the following reactions are redox reactions:

4 B C l_{3} (g) + 3 L i A l H_{4} (g) \to 2 B_{2} H_{6} (g) + 3 L i C l (s) + 3 A l C l_{3} (s)

Q. Justify that the following reactions are redox reactions:

2 K (s) + F_{2} (g) \to 2 K^{+} F^{-} (s)

Which of the following is not an example of redox reaction?
(a) $C u O + H_{2} \to C u + H_{2} O$
(b) $F e_{2} O_{3} + 3 C O \to 2 F e + 3 C O_{2}$
(c) $2 K + F_{2} \to 2 K F$
(d) $B a C l_{2} + H_{2} S O_{4} \to B a S O_{4} + 2 H C l$

Q. The following reaction is an example of a:

4 N H_{3} (g)

5 O_{2} (g)

\to

4 N O (g)

6 H_{2} O (g)

(i) displacement reaction
(ii) combination reaction
(iii) redox reaction
(iv) neutralisation reaction

Q. Given

4 N H_{3} (g) + 5 O_{2} (g) \to 4 N O (g) + 6 H_{2} O (g)

The above reaction is an example of:
(i) displacement reaction
(ii) combination reaction
(iii) redox reaction
(iv) neutralisation reaction

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Justify that the following reactions are redox reactions: (a) CuO(s) + H2(g) → Cu(s) + H2O(g) (b) Fe2O3(s) + 3CO(g) → 2Fe(s) + 3CO2(g) (c) 4BCl3(g) + 3LiAlH4(s) → 2B2H6(g) + 3LiCl(s) + 3 AlCl3 (s) (d) 2K(s) + F2(g) → 2K+F– (s) (e) 4 NH3(g) + 5 O2(g) → 4NO(g) + 6H2O(g)