What volume in ml would you need to prepare 500 ml of a...

Question

What volume in ml would you need to prepare 500 ml of a 50 mM solution of Tris (MWT 121 g/mol) from 1L of a 1M stock?

Answer 1

The molar mass of Tris is not needed for these calculations.  You can simply use the expression M1V1 = M2V2 where M and V are the molarity and volume respectively and 1 and 2 are the initial and final solutions respectively.  The units must be the same however.  So we can change 50 mM to 0.05 M (to have M on both sides of the equation).

M1 = 1 M

V1 = x

M2 = 0.05 M

V2 = 500 ml

(1 M)(x ml) = (0.05 M)(500 ml)

x = 25 mls

So, you need to take 25 mls of the 1 M solution and dilute it to a final volume to 500 mls.

NOTE:  the fact that you have 1 L of the 1 M is not relevant.  As long as you have at least 25 mls of 1 M you can do this.