What mass (nearest integer) of phosphoric acid, H3PO4 is required to prepare 550 mL of 0.40N solution? (assuming complete neutralisation of acid)
The complete neutralization of H3PO4 means it will act as a tribasic acid.
0.40NH3PO4 corresponds to 0.403 MH3PO4.
1L of solution will contain
0.403 moles.
550 mL of solution will contain
0.40×5503×1000 moles.
This corresponds to H3PO4=0.40×550×983×1000=7.187 g.
The nearest integer is 7.