Question

Chem Lab/Biology Question

You need to prepare 350ml of an extraction buffer with the following composition: 125 mM NaCl (MW=58.44), 100mM Tris base (MW=121.1), and 3% (w/v) sodium dodecyl sulfate. You have access to water, powdered Tris base, 6 M NaCl solution, and 40% (w/v) solution of sodium dodecyl sulfate. How much of each component is needed (you may assume that solids contribute negligible volume to a solution)?

Answer 1

Solution :-

We want to make the 350 ml solution that is 0.350 L

So

Lets find the volume of the 40 % w/v solution needed to make 3% w/v solution

3 % w/v means 3 g solute in 100 ml solution

Therefore

350 ml * 3 % / 100 ml = 10.5 g sodium dodecyl sulfate is needed

So the volume of the 40 % solution needed is

40 % means 40 g in 100 ml

So 10.5 g * 100 ml / 40 % = 26.25 ml

So we need 26.25 ml of 40 % sodium dodecyl sulfate

Now lets calculate the mass of the tris base needed

100 mM * 1 M / 1000 mM = 0.100 M

0.100 mole L * 0.350 L = 0.035 mol

0.035 mol * 121.1 g per mol = 4.239 g tris base

So we need 4.239 g tris base

Now lets calculate the volume of the 6M NaCl solution needed

125 mM * 1 M / 1000 mM =0.125 M

M1V1=M2V2

V1= M2V2/M1

     = 0.125 M * 350 ml / 6 M

     = 7.292 ml 6 M NaCl

So we need 7.292 ml 6 M NaCl

We need to use, following method to make the desired solution.

26.25 ml sodium dodecyl sulfate + 4.239 g tris base + 7.292 ml 6M NaCl mix them and dilute with distilled water to total volume of 350 ml