Question

i have a 5 M stock solution of kcl and i need a 400mM working concentration (1x). if i want to make a 10 ml of a 2x concentration, how much 5 M stock and how much water do i need to add together

Answer 1

8.4 ml of water is needed to make a 10 ml of a 2x concentration.

Step-by-step explanation:

From question,

`M1= 5M,`

`M2= 400mM * 2 (2 * solution) =0.8M,`

`V2= 10ml`

`V1=  ((M2 * V2))/(M1)`

This gives
`V1 = 1.6 ml`

V1 is the available volume of water in the stock solution.

To obtain 10ml of 2x concentration, the volume of water required is:
`10-1.6 =8.4ml`of water.

Hence 8.4 ml of water is needed to make a 10 ml of a 2x concentration.