Question

A solution is made by dissolving 0.4352g of nickel through water to make a 500.0 mL solution. A dilution is made by pipeting 2.00 mL into a 250.0 mL volumetric flask and bring it to volume with distilled water. What is the parts per million, ppm, concentration of nickel in the dilution?

Answer 1

We know that 1 ppm = 1 mg/L

The concentration of the stock solution is = 0.4352 g / 500.0 mL

                                                            = 0.4352x10³ mg / 0.5 L

                                                            = 870.4 mg/L

                                                            = 870.4 ppm

So the concentration of 2.00 mL stock solution is also 870.4 ppm

According to law of dilution   MV = M'V'

Where M = Molarity of stock = 870.4 ppm

V = Volume of the stock = 2.0 mL

M' = Molarity of dilute solution = ?

V' = Volume of the dilute solution = 250.0 mL

Plug the values we get   , M' = MV /V'

                                          = ( 870.4 x 2.0) / 250.0

                                          = 6.963 ppm

Therefore the concentration of the dilute solution is 6.963 ppm