[_cheers]

Given that the stepwise dissociation constants for phosphoric acid are:
Ka1 = 7.5×10-3; Ka2 = 6.2×10-8; Ka3 = 4.8×10-13

To prepare 1.30 L of a buffer solution having an ionic strength of 0.150 and a pH of 7.00 would require:

(mass) of Na2HPO4(anhydrous) and

      
(mass) of NaH2PO4(anhydrous).

For the purpose of keeping this exercise relatively simple, we assume  that the activity coefficients are all unity.

Ok, im not even sure where to start on this and Im not sure what is meant by unity...direction pls? ty

   

[AWK]

Ok, im not even sure where to start on this and Im not sure what is meant by unity...direction pls? ty

Use concetrations in buffer calculation