Experiment 17: Colorimetric Analysis for AP Chemistry
For a quick review on stoichiometry, refer to the following concepts:
- Moles, Molar Mass, and Molarity for AP Chemistry
- Percent Composition and Empirical Formulas for AP Chemistry
- Reaction Stoichiometry for AP Chemistry
- Limiting Reactants for AP Chemistry
- Percent Yield for AP Chemistry
This experiment involves determining the amount of a substance in a solution. A calibration curve is constructed plotting the measured absorbance versus the concentration of a colored substance. The concentration of an unknown solution may be determined by reversing this process. (See the Stoichiometry chapter.)
- support stand
- test tube(s) or cuvettes
Using either a pipet or a buret, quantities of standard solutions are measured. (If a buret is used, separate measurements of the initial and final volumes are needed.) Solvent may be added to dilute the samples if needed. These are the known solutions from which a calibration curve will be constructed.
The absorbance of each solution is determined with a spectrophotometer.
The absorbance of one or more unknown solutions is determined with a spectrophotometer.
Concentrations of the known solutions are calculated using the dilution equation.
A plot of absorbance versus concentration for the known solutions is made.
The plot allows the absorbance of the unknown solution(s) to be converted to concentration.
Any colored substance may be used.
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