Question

How would you prepare 10 ml of a 0.25% m/v hcl solution if 1% m/v hcl was available? how much 1% m/v hcl is needed? how much distilled water is used?

Answer 1

To solve this we use the equation, 

M1V1 = M2V2

where M1 is the concentration of the stock solution, V1 is the volume of the stock solution, M2 is the concentration of the new solution and V2 is its volume.

M1V1 = M2V2

1% x V1 = 0.25% x 10 mL

V1 =2.5 mL

Therefore, you will need to have 2.5 mL of the 1% HCl solution and 7.5 mL of distilled water. In mixing the two liquids, you should remember that the order of mixing would be acid to water. So, you use a 10 mL volumetric flask . Put small amount of distilled water and add the 2.5 mL of HCl solution. Lastly, dilute with distilled water up to the 10 mL mark.