Experiment: Determination of iron in multi-vitamin tablets by colorimetry 1. Wha

Question

Experiment: Determination of iron in multi-vitamin tablets by colorimetry

1. What is the function of ascorbic acid in this experiment?

2. Briefly outline how would you use this method to determine relative concentration of different species of Fe (i.e. Fe(ii) and Fe(iii) oxidation states in the same solution ), for example in lake water to monitor red-ox environments?

3. What is a t-test and how will you use it to analyze the concentration of iron in your samples?

Experiment 6. Determination of iron in multi-vitamin tablets b colorimetry and verification of their consistency between two production batches. Suggested Reading: Quantitative Chemical Analysis by Daniel C. Harris, 9h edition, Chapter 4, 18, 19 PRELAB QUESTIONS 1. What is the function of ascorbic acid in this experiment? 2. Briefly outline how would you use this method to determine relative concentration of different species of Fe (ie. Fe(ii) and Fe(iii) oxidation states in the same solution for example in lake water to monitor red-ox environments? 3. What is a t-test and how will you use it to analyze the concentration of iron in your samples?

Explanation / Answer

In the determination of iron in multivitamin tablet

1. Ascorbic acid is used to reduce the dissolved Fe3+ from the tablets to Fe2+ which is then determined by complex formation in colorimetry in the next step.

2. The samples are first treated with ascorbic acid, wherein, Fe3+ is reduced to Fe2+. the Fe2+ formed is then complexed with say bipyridyl and then the complex concentration is determined by colorimetry. the amount of complex formed is directly proportional to the amount of Fe2+ in solution. The Fe3+ in solution in turn forms complex with NaSCN and the complex thus formed absorbs at completely different wavelength in the colorimetry experiment. Thus the relative amounts of the two Fe3+ and Fe2+ can be determined by using colorimetry.

3. test sample is the one which does not have any sample to be tested for Fe content but has the complexing agent and is used as the blank run. this is then subtracted from the actual runs of the sample to get absolute values for the Fe content in the samples.

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