I have a 0.00156 M solution of CuSO4*5H2O in water (from 0.0398 g of CuSO4*5H20 in 100 mL of water). How would I calculate the ppm of Cu of that solution from that information?

Answer 1

You have 0.0398 g CuSO4.5H2O. Convert that to g Cu as follows:
0.0398 x (atomic mass Cu/molar mass CuSO4.5H2O) = ?
That gives you g Cu/100 mL (technically, that should be 100 mL OF SOLUTION. Then convert 0.0398 g Cu to mg Cu which is in 100 mL of solution then multiply by 10 to find mg Cu/L of solution and that is ppm of Cu.

Answer 2

Now if I were to find ppm of Cu in different aliquots of this stock solution (5 mL, 10 mL, etc.) how would I go about that?