Answer to Question #212765 in Physical Chemistry for Arvin

Question

You are asked to prepare a buffer solution with a pH of 3.50. The following solutions, all 0.100 M, are available to you: HCOOH, CH₃COOH, H₃PO₄ , NaCHOO, NaCH₃COO, and NaH₂PO₄. 

What would be the best combination to make the required buffer solution?

What ratio of [conjugate base]/[acid] would yield the best result for the required buffer solution created in the question above?

Answer 1

HCOOH and HCOONa

The best ratio is 0.569

PH=pKa +log (HCOONa/HCOOH)

3.5= log (1.8× 10^-4) + log (HCOONa/HCOOH)

Log (HCOONa/ HCOOH)= 3.5 - 3.745

HCOONa/HCOOH =0.569