Answer:
20mL of the stock solution and dilute to 100mL
Explanation:
20mM = 0.020M is the concentration of the diluted solution. As you want to prepare this solution from a 0.1M solution, dilution factor is:
0.1M / 0.020M = 5
That means you need to dilute the stock solution 5 times to obtain the 20mM sucrose solution.
As you want to prepare 100mL, you need to add:
100mL / 5 =
20mL of the stock solution and dilute to 100mL
