Generating and Using a Calibration Graph
Solution Dilution!
Now that you've taken absorbance spectra and plotted absorbance vs. wavelength, it's time to make a calibration graph, and plot absorbance vs. concentration. First though, you'll need solutions of different concentrations, and to do that, you need to make dillutions.
Dillution measurments use the equation:
Where M1 is the molarity of the first solution and M2 is the molarity of the second, and V1 and V2 are the volumes.
This is actually a condensed equation of two molarity equations. Let's walk through how it comes to this.
You want to make a 50mL of a 0.03M solution. You have a 0.1M solution.
We can start with the Molarity Equation
Start with what you want. You want 50mL of a 0.03M solution. You have a volume and a concentration so you can find how many moles of your compound will be in there. Try doing this!
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Now that you know the number of moles you need, now you need to find a volume of your current solution, that has that many moles in it. Your current solution is 0.1M So how many mL would you need, to have that many moles?
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Now that you found how many mL of your stock solution you need, how many mL of water will you need to add?
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That was the long way of doing this problem. You can also use the simplified equation of
You want 50mL of a 0.03M solution. You have a volume and a concentration for one of the solutions, so that will go on one side
M1 = 0.03M
V1 = 50mL
You also have the concentration of the other solution. You have a stock solution of 0.1M
M2 = 0.1M
Now that you've worked through a problem, try some additional practice problems!
