Chapter 2, Problem 25P

Summary Introduction

To determine: The weight in grams of sodium dihydrogen phosphate (NaH₂PO₄∙H₂O; FW 138) and disodium hydrogen phosphate (Na₂HPO₄; FW 142) needed to prepare 1L of a standard buffer at pH 7.00 with a total phosphate concentration of 0.100 M.

Introduction:

The pH of the internal fluid of the cells is maintained by the phosphate buffer system. The buffer comprises of dihydrogen phosphate ions and hydrogen phosphate ions. The addition of extra hydrogen ion in the fluid of the cellular region, results in change in pH which is then neutralized by the hydrogen phosphate ion. Similarly, the change in pH caused by the action of the hydroxide ions is neutralized by the dihydrogen phosphate ion.