Justify that the following reactions are redox reactions:

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

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


In BCl3, B = + 3 and Cl = -1


In LiAlH4, Li = + 1, Al = + 3 and H = -1


In B2H6,B = -3 and H = + 1


In LiCl, Li = + 1 and Cl = -1


In AlCl3, Al = + 3 and Cl = -1


In this reaction, O.N. of B decreases from + 3 in BCl3 to -3 in B2H6 i.e. BCl3 is reduced to B2H6. Also, the O.N. of H increases from -1 in LiAlH4 to + 1 in B2H6 i.e. is LiAlH4 oxidised to B2H6.


Hence, the given reaction is a redox reaction.


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