How many ml of a 0.50m solution of hno3 solution are needed to make 500 ml of 0.15m hno3

150.0 mL.

Explanation:

It is known that the no. of millimoles of HNO₃ before dilution = the no. of millimoles of HNO₃ after dilution.

∵ (MV) before dilution = (MV) after dilution.

∴ V before dilution = (MV) after dilution / M before dilution = (0.15 M) (500.0 mL) / (0.50 M) = 150.0 mL.