Question

What is the equilibrium constant for the following reaction:HCO2H(aq) + CN–(aq) HCO2–(aq) + HCN(aq)Does the reaction favor the formation of reactants or products? The acid dissociation constant, Ka, for HCO2H is 1.8 x 10–4and the acid dissociation constant for HCN is 4.0 x 10–10.(A) K = 1.00. The reaction favors neither the formation of reactants nor products.(B) K = 2.2 x 10–6. The reaction favors the formation of products.(C) K = 2.2 x 10–6. The reaction favors the formation of reactants.(D) K = 4.5 x 105. The reaction favors the formation of products.(E) K = 4.5 x 105. The reaction favors the formation of reactants.

Answer 1

Answer:

(D) K = 4.5 x 10⁵. The reaction favors the formation of products

Explanation:

HCOOH + CN⁻ ⇆ HCOO⁻ + HCN

K = [HCOO⁻] [ HCN ] / [ HCOOH] [ CN⁻]

HCOOH ⇄ H ⁺ + COO⁻

K₁ = [ H⁺] [ COO⁻ ] / [HCOOH ]

HCN ⇆ H⁺ + CN⁻

K₂ = [ H⁺] [ CN⁻] / [ HCN ]

K₁ / K₂

= [ H⁺] [ COO⁻ ] / [HCOOH ]  X  [ HCN ] / [ H⁺] [ CN⁻]

= [ COO⁻ ][ HCN ] / [HCOOH ]  [ CN⁻]

= K

K = K₁ / K₂

= 1.8  x 10⁻⁴ / 4 x 10⁻¹⁰

= 4.5 x 10⁵

So equilibrium constant of the reaction

HCOOH + CN⁻ ⇆ HCOO⁻ + HCN

is very high . Hence reaction favours the formation of product.

option (D) is correct.