“Making solutions with multiple components” Part II: Making solutions from concentrated stock solutions

Often, solutions containing multiple components are prepared from concentrated stock solutions… Stock solutions vary in their concentrations, and in the units used to express their concentrations, but are all used in the same way… 10X TBE 70% Glycerol 5 M NaCl

To prepare solutions for use in the lab, stock solutions are DILUTED to the correct working concentration… Suppose I need to make 5 L of 0.05 M NaCl from a 5 M NaCl stock solution… and enough water to make 5 L total solution I will need to add some volume of 5 M NaCl… Let’s figure out what volume of NaCl stock we need… 5 L 5 M NaCl

What volume of NaCl stock do I add? Use C1V1 = C2V2 C1 = 5 M C2 = 0.05 M V1 = ? V2 = 5 L = 5000 mL V1 = (0.05 M)(5000 mL) 5 M V1 = 50 mL and enough water to make 5 L total solution I will need to add 50 mL of 5 M NaCl… 50 mL 5 L Let’s make the solution… 5 M NaCl

Let’s make the solution… and enough water to make 5 L total solution I will need to add 50 mL of 5 M NaCl… 5 L 5 M NaCl 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: CG 50 mM calcium chloride 15% glycerol This is ONE solution with multiple components that we will make from the following stock solutions: 1 M CaCl2 60% Glycerol

Making 500 mL of CG from concentrated stock solutions… and enough water to make 500 mL total solution I will need to add some volume of 1 M CaCl2… 500 mL and some volume of 60% glycerol 1 M CaCl2 H2O 60% Glycerol Let’s do the math…

What volume of 1 M CaCl2 do I need? Use C1V1 = C2V2 C1 = 1 M = 1000 mM C2 = 50 mM V1 = ? V2 = 500 mL V1 = (50 mM)(500 mL) 1000 mM V1 = 25 mL and enough water to make 500 mL total solution 500 mL and some volume of 60% glycerol I will need to add 25 mL of 1 M CaCl2… H2O 25 mL 1 M CaCl2 60% Glycerol Let’s continue…

What volume of 60% Glycerol do I need? Use C1V1 = C2V2 C1 = 60% C2 = 15% V1 = ? V2 = 500 mL V1 = (15%)(500 mL) 60% V1 = 125 mL and enough water to make 500 mL total solution 500 mL and 125 mL of 60% glycerol I will need to add 25 mL of 1 M CaCl2… 125 mL H2O 25 mL 1 M CaCl2 60% Glycerol Let’s finish…

Let’s make our solution… and 125 mL of 60% glycerol H2O I will need to add 25 mL of 1 M CaCl2… 500 mL …to enough water to make 500 mL total solution Done! CG