Question

1.5mL of a 0.05M solution of calcium chloride (CaCl2) was diluted with water to a volume of 10L. What was the concentration of Cl- ions in the diluted solution in ppm.

Answer 1

mols CaCl2 = M x L = (1.5/1000) x 0.05 = approx 7E-5 but you need a better number than that.
Convert to grams CaCl2 = mols x molar mass = approx 0.008. Again, you must get a better number. Convert to grams Cl.
Thats 0.008 g CaCl2 x (2*35.5/111) = approx 0.05 g Cl^-.

1 ppm = 1 mg/L. You have approx 50mg/10 L = ? ppm
Check my work.