molarity x volume = moles volume = moles/molarity Pb(NO3)2 is the dissolved chemical so every mole of this gives a mole of Pb2+ 0.0500 mol Pb2+ / (2.50 mol Pb2+/L) = 0.0200 L, or 20.0 mL Solution molarity x volume = moles volume = moles/molarity Pb(NO3)2 is the dissolved chemical so every mole of this gives a mole of Pb2+ 0.0500 mol Pb2+ / (2.50 mol Pb2+/L) = 0.0200 L, or 20.0 mL.