Question

2. A stock solution of 1.24 x 10^-4 M dye is available in the laboratory. What volume of the stock solution must be transferred to the volumetric flask to prepare a 25.00 mL dilution with a concentration of 2.00 x 10^-5 M?

3. Perhaps the volume in question 2 is an inconvenient fractional amount. What volume should the analyst dispense to simplify the preparation of the dilution?

Answer 1

2)

Given data,

Volume = 25.00 mL

Concentration = 2 x 10^-5

1000 ml contains 2 x 10^-5 Moles

25 ml contains ----> = 2 x 10^-5 * 25 / 1000

= 0.05 x 10^-5 moles

1000 ml contains ------> 1.24 x 10^-5 moles

?? ------------>  0.05 x 10^-5 moles

=  0.05 x 10^-5 x 1000 ml / 1.24 x 10^-5

= 0.0005 / 1.24 x 10^-5

= 40.32 mL