Lead is a toxic metal that affects the central nervous system. A Pb-contaminated water sample contains 0.0012% Pb by mass. How much of the water in milliliters contains 145 mg of Pb? (Assume that the density of the solution is 1.0g/mL.)

Answer 1

So from density we know that
.0012 g/100 mL
Converting g into mg
0.0012% = 0.0012 g/100 ml water, or 1.2 mg

so for 145 mg, you need
145mg Pb *100mL/1.2mg Pb = 12083 ml water or 12.083 L of water