Question

For a pharmalogical experiment you need 1L of a drug at a concentration of 10x10-6 in saline. You have aliquots of a stock solution at a concentration of 10mM. How do you make the working solution?

Answer 1

                            Stock solution                                    required solution

concentration = M1= 10mM = 10 x10^-3M =10^-2M       concentration = M2= 10 x10^-6M = 10^-5M

Volume = V1=                                                                  volume = V2 = 1L = 1000 mL

for dilution

M1V1=M2V2

10^-2 x V1 = 10^-5 x 1000

V1 = 1 mL

we take 1mL of 10mM stock solution and add 999 mL of water to convert 1000mL (Or) 1L of dilution solution