How would you prepare 10.0 Liters of a solution that was 20 parts per million sodium perchlorate in water? What would be the molarity of the solution (assume density is 1.0 g/mL and 1ppm=1 mL/L)?

Answer 1

20 ppm = 20 mg NaClO4/L
10 L would be 200 mg NaClO4/10 L.
I would weigh 200 mg NaClO4 and dump it into 10L water. (That isn't quite right since it is mg/L soln and not mg/L H2O so if it is done right, you would weigh 200 mg NaClO4, dissolve it in some water, then make to a final volume of 10.0L).

M = ?
20 mg/L is 0.02 g/L
0.02 g = ? mols.
0.02/molar mass NaClO4