An experiment was conducted to determine the lead content of 10.00 g sample of shark meat. The meat was  dissolved in 20.00mL of 1.00 M hydrochloric acid (HCl) to which 30mL  of water was added to dilute the sample.
The resulting solution was filtered and 10.00 mL of the filtrate was mixed with 20.00 mL of a solution that gave a coloured solution as it reacted with the lead ions. In the final mixture, lead from the shark meat was present as Pb²⁺(aq). Using a UV-visible colorimeter, the absorbance of this final solution was measured using a 2.00 mL sample. The absorbance was 0.110.

Absorbances of standard solutions were also obtained, as shown below

Using the above data and the graph paper provided, construct a calibration curve.

• What was the concentration percentage (m/v) of lead ions in the final mixture?

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• What was the concentration percentage (m/m) of lead in the original sample?

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• What is the concentration of lead ions in the original sample in ppm?

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• Determine the mole of lead ions present in the original sample of shark meat.

• What was the molarity of lead in the solution made by dissolving the shark meat  in 20.00 mL of 1.00 M HCl (hydrochloric acid) and 30 mL of water?                                                                       

• a) Using a UV-visible colorimeter, as outlined above, is it necessary to:
• know the molarity of the HCl used to dissolve the shark meat? Explain

• know the wavelength of light used? Explain

• When is it necessary to dilute the sample before inserting it in the spectrometer?           

• Why are calibration curves necessary for each investigation?

• In quantitative analysis which is more accurate, atomic absorption, UV‑visible spectroscopy or infrared spectroscopy. Explain.

• Which of the following techniques uses a calibration curve?
• Atomic absorption spectroscopy
• Uv-visible spectroscopy
• Mass spectroscopy
• Infrared spectroscopy

• Which of the following techniques uses a reference cell?
• Atomic absorption spectroscopy
• UV-visible spectroscopy
• Mass spectroscopy
• Infrared spectroscopy

• What is the purpose of a reference cell?

Solution