Answer to Question #234622 in General Chemistry for Nana

Question

Consider a buffer solution made up of H₂PO₄^- and HPO₄^2-. What mole ratio of HPO₄^2- / H₂PO₄^- will give a pH of 6.95? K_a = 6.3 x 10^-8

Answer 1

pH = pKa + Log₁₀(base/acid)

-log 6.3 × 10^-8 = 7.3

Therefore, log₁₀(base/acid) = pH-pKa

= 6.95 -7.3 = -0.08

= 10^0.08 = 0.832

or 1/0.832 = 1.2