What is the pH of a buffer solution???? CAN ANYONE HELP ME WITH PROBLEM!!!!!?

Question

Consider an acid, HA, with pKa = 5.33. What is the pH of a buffer solution made up by mixing a 0.446M solution of the acid with an equal volume of a 0.78M solution of its salt?

Can Anyone Help ME!!!! PLZ!!!!

Answer 1

Since you mix equal volumes, the acid and salt concentration is halved. So

Apparent concentration of the acid

[HA] = (1/2) · 0.446M = 0.223M

Concentration of ions form dissociated salt

[A⁻] = (1/2) · 0.78M = 0.39M

The use Henderson-Hasselbalch equation:

pH = pKa + log( [A⁻]/ [HA] )

= 5.33 + log( 0.39 / 0.223

= 5.57