You wish to construct a buffer of pH=7.0. Which of the following weak acids (w / corresponding conjugate base) would you select?

A.) HClO2 Ka=1.2x10^-2

B.) HF Ka=7.2x10^-4

C.) HOCl Ka=3.5x10-8

D.) HCN Ka=4.0x10^-10

Question

Jada Charles

Chemistry

21 October, 04:26

You wish to construct a buffer of pH=7.0. Which of the following weak acids (w / corresponding conjugate base) would you select?

A.) HClO2 Ka=1.2x10^-2

B.) HF Ka=7.2x10^-4

C.) HOCl Ka=3.5x10-8

D.) HCN Ka=4.0x10^-10

+3

Answers (1)

Know the Answer?

Aaron · Answer 1

C.) HOCl Ka=3.5x10^-8

Explanation:

In order to a construct a buffer of pH = 7.0 we need to find the pKa values of all the acids given below

we Know that

pKa = - log (Ka)

therefore

A) pKa of HClO2 = - log (1.2 x 10^-2)

=1.9208

B) similarly PKa of HF = - log (7.2 x 1 0^-4) = 2.7644

C) pKa of HOCl = - log (3.5 x 1 0^-8) = 7.45

D) pKa of HCN = - log (4 x 1 0^-10) = 9.3979

If we consider the Henderson - Hasselbalch equation for the calculation of the pH of the buffer solution

The weak acid for making the buffer must have a pKa value near to the desired pH of the weak acid.

So, near to value, pH=7.0., the only option is HOCl whose pKa value is 7.45.

Hence, HOCl will be chosen for buffer construction.

You wish to construct a buffer of pH=7.0. Which of the following weak acids (w / corresponding conjugate base) would you select?A.) HClO2 Ka=1.2x10^-2B.) HF Ka=7.2x10^-4C.) HOCl Ka=3.5x10-8D.) HCN Ka=4.0x10^-10

You wish to construct a buffer of pH=7.0. Which of the following weak acids (w / corresponding conjugate base) would you select?

A.) HClO2 Ka=1.2x10^-2

B.) HF Ka=7.2x10^-4

C.) HOCl Ka=3.5x10-8

D.) HCN Ka=4.0x10^-10