Keq calculation

Question

Calculate each equilibrium constant (Keq) given pKa data (find pKa if needed)

Benzoic acid pKa = 4.19

Benzocaine pKa = ~2.5 (CA)

9-Fluorenone pKa = ~43/Na

 

1. benzoic acid + naoh = sodium benzoate + H2O

2. benzocaine + hydronium hcloride = benzocaine hydrochloride + H2O

Answer 1

The the relationship between K_eq​ and ΔpK_a

K_eq​ =10^ΔpKa

1. Reaction of Benzoic Acid with NaOH

Benzoic Acid + NaOH ⇔ Sodium benzoate + H₂​O

ΔpK_a= ​pK_a of water​−pK_a of benzoic acid​ = 15.7-4.19= 11.51

K_eq​=10^11.51

1. Reaction of Benzocaine with Hydrochloric Acid

Benzocaine + H_3​O⁺ ⇌ Benzocaine hydrochloride + H₂​O

ΔpK_a= ​pK_a of benzocaine hydrochloride​−pK_a of H3O+​ = 2.5- (-1.7)= 4.2

K_eq​=10^4.2