Question

Choose the disproportionation reaction among the following redox reactions.
(a) 3Mg (s) + N2 (g) → Mg3N2 (s)
(b) P4 (s) + 3 NaOH+ 3H2O → PH3(g) + 3NaH2PO2 (aq)
(c) Cl2 (g)+ 2KI(aq) → 2KCl(aq) + I2
(d) Cr2O3 (s) + 2Al (s) → Al2O3(s) + 2Cr(s)

Answer 1

a redox reaction, the species is simultaneously oxidized and reduced to form at least two different products is known as disproportionation redox reaction.
disproportionation reaction can be represented by , 2A ⇒A' + A" , Where A, A' and A" are different chemical species.

Answer :- option (b)
Explanation :- P₄ ------>PH₃ + NaH₂PO₂
Here you can see oxidation state of P is different in all three molecules.
oxidation state of P in P₄ = 0
oxidation state of P in PH₃ = -3
oxidation state of P in NaH₂PO₂ = +5
Also P is oxidized as well as reduced in same reaction.
So, it is disproportionation redox reaction.