“Making solutions with multiple components”

Part II: Making solutions from concentrated stock solutions

Often, solutions containing multiple components are prepared from concentrated stock solutions…

10X TBE

5 MNaCl

70% Glycerol

Stock solutions vary in their concentrations, and in the units used to express their concentrations, but are all used in the same way…

5 MNaCl

Suppose I need to make 5 L of 0.05 M NaCl from a 5 M NaCl stock solution…

I will need to add some volume of 5 M NaCl…

5 L

To prepare solutions for use in the lab, stock solutions are DILUTED to the correct

working concentration…

and enough water to make 5 L total solution

Let’s figure out what volume of NaCl stock we need…

Use C1V1 = C2V2

C1 = 5 MC2 = 0.05 MV1 = ?V2 = 5 L = 5000 mL

V1 = (0.05 M)(5000 mL)5 M

V1 = 50 mLI will need to add 50 mL of 5 M NaCl…

5 L

What volume of NaCl stock do I add?

and enough water to make 5 L total solution

Let’s make the solution…

5 MNaCl

50 mL

I will need to add 50 mL of 5 M NaCl…

Let’s make the solution…

and enough water to make 5 L total solution

5 MNaCl

5 L

0.05 M

NaCl

Done!

Now let’s make a solution containing two solutes from concentrated stock solutions…

Here is a simple solution containing multiple components:

CG50 mM calcium chloride

15% glycerol

This is ONE solution with multiple components that we will make from the following stock solutions:

1 MCaCl2

60%Glycerol

I will need to add some volume of 1 M CaCl2…

Making 500 mL of CG from concentrated stock solutions…

and enough water to make 500 mL total solution

Let’s do the math…

1 MCaCl2

500 mL

60%Glycerol

and some volume of 60% glycerol

H2O

I will need to add 25 mL of 1 M CaCl2…

What volume of 1 M CaCl2 do I need?

and enough water to make 500 mL total solution

Let’s continue…

1 MCaCl2

500 mL

60%Glycerol

and some volume of 60% glycerol H2O

Use C1V1 = C2V2

C1 = 1 M = 1000 mMC2 = 50 mMV1 = ?V2 = 500 mL

V1 = (50 mM)(500 mL) 1000 mMV1 = 25 mL

25 mL

I will need to add 25 mL of 1 M CaCl2…

What volume of 60% Glycerol do I need?

and enough water to make 500 mL total solution

Let’s finish…1 MCaCl2

500 mL

60%Glycerol

and 125 mL of 60% glycerol

H2O

Use C1V1 = C2V2

C1 = 60%C2 = 15%V1 = ?V2 = 500 mL

V1 = (15%)(500 mL) 60%V1 = 125 mL

25 mL

125 mL

I will need to add 25 mL of 1 M CaCl2…

…to enough water to make 500 mL total solution

Done!

500 mL

and 125 mL of 60% glycerol

H2O

CG

Let’s make our solution…