A very useful equation for calculating dilutions is C1V1=C2V2
C1 = the concentration of your stock solution
V1 = the volume of the stock solution you will use
C2 = the concentration you want after dilution
V2 = the volume of the final diluted solution
You have a stock solution of 20% SDS. You need 500 mL of 5% SDS. How much of the 20% SDS stock do you need?
We can solve this using the dilutions equation, C1V1=C2V2
C1 = the concentration of your stock solution = 20%
V1 = the volume of the stock solution you will use = what we want to figure out
C2 = the concentration you want after dilution = 5%
V2 = the volume of the final diluted solution = 500 mL
Plugging in the values, we have
20% V1 = 5% (500 mL)
V1 = 5% (500 mL) / 20%
V1 = 125 mL
To make the 5% solution, you’d take 125 mL of 20% stock, and add dH2O to a total volume of 500 mL.
You have a stock solution of 100 mg/mL ampicillin. You need 10 mL of 1 mg/mL ampicillin. How much of the 100 mg/mL ampicillin stock do you need?
We can solve this using the dilutions equation, C1V1=C2V2
C1 = the concentration of your stock solution = 100 mg/mL
V1 = the volume of the stock solution you will use = what we want to figure out
C2 = the concentration you want after dilution = 1 mg/mL
V2 = the volume of the final diluted solution = 10 mL
Plugging in the values, we have
100 mg/mL V1 = 1 mg/mL (10 mL)
V1 = 1 mg/mL (10 mL) / 100 mg/mL
V1 = 0.1 mL = 100 μL
To make the 1 mg/mL solution, you’d take 100 μL of 100 mg/mL stock, and add dH2O to a total volume of 10 mL.
If you take 200 mL of 1 M NaCl, and dilute it with dH2O to a total volume of 500 mL, what is the final concentration of NaCl in the dilution?
We can solve this using the dilutions equation, C1V1=C2V2
C1 = the concentration of your stock solution = 1 M
V1 = the volume of the stock solution you will use = 200 mL
C2 = the concentration after dilution = what we are solving for
V2 = the volume of the final diluted solution = 500 mL
Plugging in the values, we have
1 M (200 mL) = C2 (500 mL)
C2 = 1 M (200 mL) / 500 mL
C2 = 0.4 M
The final concentration of NaCl in this dilution is 0.4 M.