Question

Construct a table to show how to make the standard solutions from serial dilution, starting with a stock solution of 1000 ppm in 100 mL volumetric flask.

Use 1000 ppm standard soltuions of Co, Cr, Pb, Cd, and Zn to prepare the following five standard solutions with 10% HNO₃ in 100 mL volumetric flask:

Std 1: 100 ppm of Co, Cr, Pb, Cd, Zn

Std 2: 50 ppm of Co, Cr, Pb, Cd, Zn

Std 3: 10 ppm of Co, Cr, Pb, Cd, Zn

Std 4: 5 ppm of Co, Cr, Pb, Cd, Zn

Std 5: 1 ppm of Co, Cr, Pb, Cd, Zn

Answer 1

Using,

C1V1 = C2V2

Initial volume of stock needed = V1 = C2V2/C1

with,

C1 and V1 are initial concentration of stock and volume of stock solution taken

V2 is the final volume of solution

So,

Std 1: 100 ppm of Co, Cr, Pb, Cd, Zn

V1 = 100 ppm x 100 ml/1000 ppm = 10 ml

So we take 10 ml of 1000 ppm stock solution and dilute with 90 ml of 10% HNO3 solution

Std 2: 50 ppm of Co, Cr, Pb, Cd, Zn

V1 = 100 ppm x 100 ml/1000 ppm = 5 ml

So we take 5 ml of 1000 ppm stock solution and dilute with 95 ml of 10% HNO3 solution

Std 3: 10 ppm of Co, Cr, Pb, Cd, Zn

V1 = 100 ppm x 100 ml/1000 ppm = 1 ml

So we take 1 ml of 1000 ppm stock solution and dilute with 99 ml of 10% HNO3 solution

Std 4: 5 ppm of Co, Cr, Pb, Cd, Zn

V1 = 100 ppm x 100 ml/1000 ppm = 0.5 ml

So we take 0.5 ml of 1000 ppm stock solution and dilute with 99.5 ml of 10% HNO3 solution

Std 5: 1 ppm of Co, Cr, Pb, Cd, Zn

V1 = 100 ppm x 100 ml/1000 ppm = 0.1 ml

So we take 0.1 ml of 1000 ppm stock solution and dilute with 99.9 ml of 10% HNO3 solution