Question

1. You are asked to weigh out 0.1479 g of Na₂SO₄ in order to make 100 mL of a 1000 ppm solution of SO₄^2-.

a. How much NaCl (FW: 58.44 g/mol) would be needed to prepare 100 mL of a 1000 ppm solution of Cl-?

b. Similarly, how much NaNO₃ (FW: 84.99 g/mol) would be needed to prepare 100 mL of a 1000 ppm solution of NO₃^-?

Answer 1

a. 1 PPM = 1 mg/

    1000 ppm = 1000 mg/L

we want to prepare 100 ml of 1000 ppm solution of Cl^-,

for that amount of Cl^- required = 100*1000/1000 = 100 mg

mass of Cl- required = 100 mg = 0.1 g

58.44 g of NaCl =35.45 g Cl-

         ?                 = 0.1 g Cl-

amount of NaCl must dissolve = 0.1*58.44/35.45 = 0.165 g

b)

we want to prepare 100 ml of 1000 ppm solution of NO3^- ,

for that amount of NO3^-required = 100*1000/1000 = 100 mg

mass of NO3^- required = 100 mg = 0.1 g

84.99 g NaNO3 = 62 g NO3^-

        ?                = 0.1 g NO3^-

mass of NaNO3 must dissolve = 0.1*84.99/62 = 0.137 g