Question

You are required to make up 500 mL of the following buffer: 50 mM NaCl, 1 % SDS, 50 uM KCl (these are the final concentrations of each component in this one buffer)
You are provided with the three separate stock solutions: 10 M NaCL 20 % SDS 0.05 M KCl
State how much of each component you add in order to achieve this:
10 M NaCL………… mL 20 % SDS…………. mL 0.05 M KCl…………… mL
Distilled H20………. mL
Final volume = 500 mL (Final concentrations of each is 50 mM NaCl, 1% SDS, 50 uM KCl)

Answer 1

Amount NaCl needed: molarity1 x volume 1 = molarity 2 x volume 2

Molarity 1 (M1) = 10 M

volume 1 (V1)= ?

Molarity 2 (M2) = 50mM= 0.05 M

volume 2 (V2) = 500mL

putting these value in equation M1V1= M2V2

10 x V1 = 0.05 x 500

V1 = 0.05 x 500   = 2.5 mL

10

So the amount of 10 M NaCl required in 500 mL buffer = 2.5 mL

Similarly amount of 20 % SDS needed to make 1% in 500 mL buffer= 25 mL

V1 = 1 x 500 = 25 mL

20

Similarly amount of 0.05 (50000) M KCl needed to make 50 micromolar KCl in 500 mL buffer= 0.5 mL

V1 = 50 x 500 = 0.5 mL

50000

The KCl, SDS and NaCl makes a total volume of 2.5 mL + 25 mL + 0.5mL = 28 mL

Volume of distilled water = 500 - 28 = 472 mL