“Making solutions with
multiple components”
Part I: Making solutions from pure reagents
Here is a simple solution containing multiple
components:
CG
50 mM calcium chloride
15% glycerol
The most confusing thing about solutions such
as these is the way they look on paper!!
This is ONE solution with multiple
components…
Making CG: Calcium chloride and glycerol are added to water
such that you make one solution with a final concentration of 50 mM calcium
chloride and 15% glycerol
Calcium chloride
Water
Glycerol
Continue..
Making CG: Calcium chloride and glycerol are added to water
such that you make one solution with a final concentration of 50 mM calcium
chloride and 15% glycerol
CG
50 mM calcium
chloride
15% glycerol
Done!
Doing the math…
• Here’s another confusing part…
• You do the calculations for solutions
containing multiple components as if you
were making several single component
solutions…
Let’s do the math…
Making CG: Calcium chloride and glycerol are added to water
such that you make one solution with a final concentration of 50 mM calcium
chloride and 15% glycerol
Let’s make 1 L
of CG…
Calcium chloride
150 mL
Glycerol comes as 100%
1 L = 1000 mL
C1V1 = C2V2
(100%) V1 = (15%)(1000 mL)
V1 = 150 mL
5.55 g CaCl2
CaCl2 FW = 111
50 mM = 0.050 M
1 L(0.050 moles)(111 g) = 5.55 g
1L
1 mole
Water
Glycerol
Continue..
Making CG:
To make 1 L of this solution, 5.55 g of calcium chloride and
150 mL of 100% glycerol were added to enough water to make 1 L total of solution.
1L
CG
50 mM calcium
chloride
15% glycerol
Done!
A common error to watch for…
• Because the calculations for multiple
component solutions are done separately
(as if you were making several single
component solutions), students
sometimes want to just mix single
component solutions together…
Don’t do this….
Step 1: Make 50 mM CaCl2
Calcium chloride
1L
5.55 g CaCl2
CaCl2 FW = 111
50 mM = 0.050 M
1 L(0.050 moles)(111 g) = 5.55 g
1L
1 mole
50 mM CaCl2
Water
Continue..
Don’t do this….
Step 2: Make 15% glycerol
150 mL
Glycerol comes as 100%
1 L = 1000 mL
C1V1 = C2V2
(100%) V1 = (15%)(1000 mL)
V1 = 150 mL
1L
15% glycerol
Water
Glycerol
Continue..
Don’t do this….
Step 3:
And combine the two…
1L
50 mM CaCl2
1L
15% glycerol
?? mM CaCl2
2L
?? % glycerol
Because..
Don’t do this….
Because…
50 mM CaCl2
What is the final concentration of
CaCl2?
C1V1 = C2V2
(50 mM)(1 L)= (C2)(2 L)
C2 = 25 mM
What is the final concentration of
glycerol?
C1V1 = C2V2
(15%)(1 L)= (C2)(2 L)
C2 = 7.5 %
15% glycerol
25 mM CaCl2
7.5 % glycerol
2L
But… I wanted 50 mM
CaCl2, 15% glycerol!!
Hmm..If you first make
two solutions of the
desired concentration,
and add them together,
you are diluting each!!