Question

I have a 5 M stock solution of KCI (For a protocol 100 mM KCl is considered "1X" concentration). If I want to make 10 ml of a 4X concentration KCl solution, how much 5 M stock and how much water do I need to add together?

Answer 1

You need 0.8 ml of 5M stock solution and you have to add 9.2 ml of water.

Step-by-step explanation:

Protocol solution (1X): 100 mM=0.1M

4X: 0.4M

The concentration of a solution is inversely proportional to the volume of a solution, so:

`M_(1)V_(1)=M_(2)V_(2)`

where:

M1= 5M stock solution

V1= amount of solution we need to collect

M2=4X solution

V2= 10 ml (volumen of 4X solution)

Therefore:

5M×V1=0.4M×10ml

V1={0.4M}{5M}10ml=0.8ml

`5M*V_(1)=0.4M*10ml\\ V_(1)=(0.4M)/(5M)10ml=0.8ml`

To make a 10 ml solution we have to add 9.2 ml of water because V2 es 10 ml.