Question

You have a stock solution consisting of 2.5L of 6.00M MgSO4. However, you need 225 mL of a 0.500 M solution. How will you dilute the solution, and how much of the stock solution will you need?

A) 20.0 mL (not the answer)
B) 9 mL
C) 18.8 mL
D) 23.08 mL

Answer 1

18.8 mL

Step-by-step explanation:

The dilution formula states that the product between the initial molarity and the initial volume should be equal to the product between the final molarity and the final volume, since the number of moles of a substance remains constant in a dilution process:

`c_1V_1 = c_2V_2`

We are given the initial molarity of the stock solution
`c_1`, the final molarity of the diluted solution
`c_2` and the final volume of the diluted solution
`V_2`.

Rearranging the expression for the volume of the stock solution, we get:

`V_1 = (c_2V_2)/(c_1) = (0.500~M\cdot 225 mL)/(6.00 M) = 18.8~mL`

Therefore, 18.8 mL of the stock solution are required.