Boston College
CHEM CH111
Experiment 6 Post Lab
1. Plotting and using the calibration curve
• Using your Excel spreadsheet, plot the calibration curve. See TECH IV, pages
37-40, for instructions. Follow th
...
Boston College
CHEM CH111
Experiment 6 Post Lab
1. Plotting and using the calibration curve
• Using your Excel spreadsheet, plot the calibration curve. See TECH IV, pages
37-40, for instructions. Follow the instructions to draw the “best fit” line
through the data points.
• Use the LINEST function to determine the slope and y-intercept. Follow the instructions in
TECH IV to find the concentration, in molarity, of your sample solution using Excel.
• Attach the spreadsheet with the plot below.
2. Determining the amount of iron in the tablet
• Calculate the concentration of iron in your original iron solution (the
solution in the volumetric flask that was obtained after the boiling and
filtration steps) in molarity. Remember, there are 2 dilution factors! See
Tro, pages 170-173 for a discussion of dilution calculations. In this case,
the unknown quantity is the initial molarity.
Questions
1. Can you think of other metals, besides iron, that are essential for human
life? Name at least three. What are some dietary sources of these other
metals?
2. In the final step of preparing the iron sample from the vitamin tablet, a
student overshot the mark on the volumetric flask. Will the absorbance of the
resulting solution be higher than, lower than or the same as it would be if the
mark was not overshot? What will be the effect on the value reported for the
amount of iron in the tablet?
Student increased the volume so he diluted the solution even more so the concentration will
be lower, therefore, the absorbance and reported amount of iron will also be lower.
Concentration is directly proportional to absorbance (Beer's law) and absorbance is directly
proportional to amount of iron.
3. List the important sources of error in this experiment and what effect each
would have on the results. Discuss in particular any errors that you may have
made.
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