Question

You weigh out pure NaH2PO4.

Weight of Sodium Dihydrogen phosphate used 0.5273 g

This is dissolved, quantitatively transfered, and diluted to 100 mL in a volumetric flask.
10 mL of this is pipetted and again diluted to 100.00 mL to make the original phosphate standard.
Calculate:

b) The phosphate concentration of this solution ______________ mM