Question

Creative Exercise: Spectrophotometry

PROMPT:

Write down as many correct, distinct, and relevant facts you can about:

To measure the iron in vegetables, iron must be extracted and complexed with 1,10-phenanthroline to create iron(II)tris(phenanthroline). An aliquot of a 50 mL sample measured in the lab was found to have an absorbance of 1.02 when measured in a cell with a path length of 1.00 cm. The molar absorptivity of iron(II)tris(phenanthroline) at 508 nm is 1.11 x 10⁴ M^-1 cm^-1.

6 statements are required for full credit. You may write more than six if you are concerned about whether each statement is distinct.

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Each statement that you provide must be distinct, correct and relevant in order to receive credit:

*Distinct requires that each statement must be different than each of your other statements and the chemical situation described above; the rephrasing of the given information or the statements that you have provided will not count.

*Correct requires that each statement is factually accurate.

*Relevant requires that each statement is relevant to the chemical situation and to content covered in this course or your prior chemistry courses. Listing facts unrelated to the chemical situation or listing facts unrelated to course content will not count for credit.

Answer 1

1. The experiment relates to the amount of iron present in the vegetables.
2. Here, the extracted iron from vegetables reacts with 1,10-phenanthroline and then forms the coloured complex (iron(II)tris(phenanthroline)).
3. the coloured complex formed is then kept in the light for the absorption of light to measure the amount of light absorbed.
4. here it can be related from the experiment that absorbance was found to be 1.02 possibly found by (A=ebc(lambart beer's law)).
5. most probable reaction for the above question.

2 Fe⁺³ + 2 NH₂OH + 2 OH ====> 2 Fe⁺² + N₂ + 4 H₂O

here, iron is first reduced to ferrous state

once the coloured complex get formed, the wavelength of light is absorbed at 508nm (400-600nm)

so as the wavelength is determines in this case the plot can be prepared between absorbance vs. concentration. then we can fine out the concentration of iron in the sample from calibration curve.

1. Lambart beer's law A=ebc, where, e=molar absorptivity, b= path length(in cm), c=concentration(mol/l)