1)Write the general equation used to determine the volume of stock required to make a given concentration of standard? Define any terms you used.
----use the 100ml flasks to create four serial dilutions of the stock 10,000uM nitrate solution that has been provided. Prepare three replicate dilutions at 5,10,20 and 40uM.
2)Using the absorbance vs concentration relationship, determine nitrate concentration for the unknown samples. Determine the concentration from the absorbance using the equation from above. Write the general equation you used to determine concentration from absorbance.
1) The general equation used to determine the volume of stock required to make a given concentration of standard is:
C1V1 = C2V2
Where:
- C1 is the initial concentration of the stock solution
- V1 is the volume of stock solution used
- C2 is the desired concentration of the diluted solution
- V2 is the final volume of the diluted solution
In this case, you are using 100ml flasks to create serial dilutions of the stock 10,000uM nitrate solution. To prepare the dilutions at 5, 10, 20, and 40uM, you would use the general equation above:
For example:
To prepare a 5uM dilution, you would solve for V1:
(10,000uM)(V1) = (5uM)(100ml)
V1 = (5uM)(100ml) / 10,000uM
V1 = 0.05ml or 50μl
Repeat this calculation for each desired concentration to determine the volume of stock solution needed for each dilution.
2) To determine the nitrate concentration for the unknown samples using absorbance, you need to establish a relationship between absorbance and concentration. This is typically done by preparing a series of known concentration solutions and measuring their absorbance using a spectrophotometer.
Once you have the absorbance vs concentration relationship, you can use the equation:
C = (A - A0) / ε
Where:
- C is the concentration of the unknown sample
- A is the measured absorbance of the sample
- A0 is the blank absorbance (absorbance of the solvent or buffer used)
- ε is the molar absorptivity (a constant specific to the analyte)
By rearranging the equation, you can determine the concentration of the unknown sample:
C = (A - A0) / ε
In this equation, you need to measure the absorbance of the unknown samples and subtract the blank absorbance. Then, divide the result by the molar absorptivity to get the concentration of the unknown samples.