5)
A student is conducting a lab that requires 2 M HCl. In the chemical closet, there is 150 mL of 8 M HCl. How much water must be added to stock solution to get the desired molarity for the lab?
A) 150 mL
B) 450 mL
C) 600 mL
D) 1200 mL

Option B. 450mL

Explanation:

To obtain the volume of water that must be added, we need to First find the volume of the diluted solution.

C1 (concentration of the stock solution) = 8M

V1 (volume of the stock solution) = 150mL

C2 (concentration of the diluted solution) = 2M

V2 (volume of the diluted solution) =?

Using the dilution formula C1V1 = C2V2, we can obtain the volume of the diluted solution as follow:

C1V1 = C2V2

8 x 150 = 2 x V2

Divide both side by 2

V2 = (8 x 150)/2

V2 = 600mL

The volume of water added is simply the difference between the volume of the diluted solution and that of the stock solution. This is illustrated below

Volume of water added = V2 - V1 = 600 - 150 = 450mL