Question

Kₐ₁ , Kₐ₂ and Kₐ₃ are the respective ionisation
constants for the following reactions.
H₂S ⇌ H⁺ + HS⁻
HS⁻ ⇌ H⁺ + S²⁻
H₂S ⇌ 2H⁺ + S²⁻
The correct relationship between Kₐ₁ , Kₐ₂ and Kₐ₃ is
(a)Kₐ₃ = Kₐ₁ x Kₐ₂
(b)Kₐ₃ = Kₐ₁ + Kₐ₂
(c) Kₐ₃ = Kₐ₁ - Kₐ₂
(d)Kₐ₃ = Kₐ₁ / Kₐ₂

Answer 1

Answer :- a)Kₐ₃ = Kₐ₁ x Kₐ₂

Answer 2

(a)Kₐ₃ = Kₐ₁ x Kₐ₂

Explanation:

H2S ⇌ H+ + HS-  (Ka1)

HS- ⇌ H+ + S2-  (Ka2)

H2S ⇌ 2H+ + S2- (Ka3)

Then Ka1 = [HS-] [H+] / [H2S]

Ka2 = [H+] [S2-] / [HS-]

Therefore Ka3 = Ka1 * Ka2

Option A is the answer.