Question

In which of the following reactions, there is no change in
valency ? [1994]
(a) 4 KClO₃ → 3KClO₄ + KCl
(b) SO₂ + 2H₂S → 2H₂O + 3S
(c) BaO₂ + H₂SO₄ → BaSO₄ + H₂O₂
(d) 3 BaO + O₂ → 2 BaO₂.

Answer 1

Answer:

number (c)BaO²+H²SO⁴=BaSO⁴+H²O²

Answer 2

answer : option (c) BaO₂ + H₂SO₄ → BaSO₄ + H₂O₂

let's check all options one - by - one.

option (a) : 4 KClO₃ → 3KClO₄ + KCl

here o.n of Cl in KClO₃ ⇒+ 1 + x + 3 × (-2) = 0

⇒x = +5

o.n of Cl in KCl = +1 + x = 0 ⇒x = -1

here we see oxidation number is changed so valency also will be change.

similarly

option (b) : SO₂ + 2H₂S → 2H₂O + 3S

o.n of s in SO₂ = +4

o.n of s in S = 0 , valency changed.

option (c) : BaO₂ + H₂SO₄ → BaSO₄ + H₂O₂

o.n of Ba in BaO₂ = +2

o.n of Ba in BaSO4 = +2

here nothing is changed. so, valency doesn't change.

option (d) : 3 BaO + O₂ → 2 BaO₂.

o.n of O in BaO = -2

o.n of O in BaO2 = -1 , valency changed.

hence, option (c) is correct.