Question

Can't figure out this question in my biochemistry prelab:

On the laboratory, two forms of sodium phosphate will be available (the monobasic monohydrate NaH2PO4 X H2O, F.W. = 137.99 g/mol, and the dibasic Na2HPO4, F.W. = 141.96 g/mol). Explain the most efficient way of making this phosphate buffer by using only ONE of the compounds, and specify which compound you will use.

Help is very much appreciated!

Answer 1

1 M sodium phosphate buffer (pH 6.0–7.2)

Mixing 1 M NaH₂PO₄ (monobasic) and 1 M Na₂HPO₄ (dibasic) stock solutions in the volumes designated in the table below results in 1 L of 1 M sodium phosphate buffer of the desired pH. To prepare the stock solutions, dissolve 138 g of NaH₂PO₄•H₂O (monobasic; m.w. = 138) in sufficient H₂O to make a final volume of 1 L and dissolve 142 g of Na₂HPO₄ (dibasic; m.w. = 142) in sufficient H₂O to make a final volume of 1 L.