Lab: Spectrophotometric Metal Ion Analysis 1. In diluting the standard solution,
ID: 878366 • Letter: L
Question
Lab: Spectrophotometric Metal Ion Analysis
1. In diluting the standard solution, 0.01M HNO3, is used. In the dilution, is it more important to use the correct volume or the correct concentration of the HNO3 solution for the dilution? Explain.
2. Will Fe3+ (aq) or Cu2+ (aq) have the shorter wavelength for maximum absorption in the visible spectrum? Explain. (Hint: Fe2+ (aq) has an orange-brown color, and Cu2+ (aq) has a blue color.)
3. An electrolytic bath sample containing the metal ion of unknown concentration contains suspended matter. Because of a lack of time, the absorbance of the sample was measured and recorded as is. As a result, will the concentration of the metal ion in the unknown be reported as too high, too low, or remain unchanged as a result of chemists hasty decision? Explain.
4. The cuvet used for the absorbance measurements is not wiped clean wth kimwipe before the absorbance measurement. As a result, will the concentration of the metal ion in the unknown be reported as too high, too low, or remain unchanged as a result of this poor technique? Explan.
Explanation / Answer
1. The absorbance of a solution is directly proportional to its concentration. Any change in concentration will affect the absorbance results. This effect is more pronounced in dilute solutions.
2. The wavelength is according to VIBGYOR. Thus, Cu2+ will have the shorter wavelength.
3. The concentration will be reported too high for the solution.
4. If not clean wiped, the concentration of solution to be measured would change, since the actual concentration would be dependent on the type of solvent or solution present before the new solution is poured into the cuvette for measurement. this would result in an error in measurement of absorbance.
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