What volume of stock solution and water is needed for the following?

You have a 5 Molar stock solution from which you wish to produce 100ml of working solution at a concentration of 200mM. Calculate the volume, in ml, of stock solution and water needed to achieve this.|||Use the dilution equation





V1M1 = V2M2





V1 = initial volume = ? ml


M1 = initial molarity = 5 M


V2 = final volume = 100 ml


M2 = final conc = 200 mM = 0.2 M





V1 = V2M2 / M1


= 100 ml x 0.2 M / 5 M


= 4 ml





You'll need 4 ml of stock solution so, assuming the volumes are additive (which you should not do really), you'll need 96 ml of water.