Answer to Question #170508 in General Chemistry for Claire

Question

The ionization constant of HA is 1.0 × 10−4 . What must be the ratio of [A−] to [HA] for the preparation of a buffer solution with a pH of 4.87?

Answer 1

In a buffer solution where HA is the weak acid/base.

HA(aq)⇌H+(aq)+A−(aq)

Given data:-

Ionisation constant (Ka)=1.0*10^-4

We know P^Ka= -logKa

So, P^Ka= -log(1.0*10^-4)=4

P^H=4.87

According to Henderson equation we get-

P^H=P^Ka +log(A^-/HA)

4.87=4+log(A-/HA)

log(A^-/HA)=4.87-4

log(A^-/HA)=.87

A-/HA=10^(. 87)

A^-/HA=7.41

Hence the ratio of [A−] to [HA] for the preparation of a buffer solution is 7.41