Question

Which of the following buffer solutions will be the best buffer for a pH of 5.0?

A. 0.25 M HCN and 0.25 M KCN
	b.	0.25 M HC2H3O2 and 0.25 M NaC2H3O2
	c.	0.25 M HClO2 and 0.25 M KClO2
	d.	0.25 M HOCl and 0.25 M NaOCl

Answer 1

if [ACID] = [SALT] , pH = pka

so that , pka of HCN = 9.31

              pKa of HC₂H₃O₂ = 4.76

              pka of HClO₂ = 1.96

              pka of HOCl = 7.46

from the above data , only    b. 0.25 M HC₂H₃O₂ and 0.25 M NaC₂H₃O₂ is suitable to form pH = 5 buffer solution.