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Can you answer question 4 & 5? The experiment and porcedure is posted below

CHM3120C Analytical Chemistry Lab Lab 7. Spectrophotometric Determination of Iron in Mohrs Salt with o-Phenanthroline Requir burette is pre-rinsed with the solution being diluted. Be sure to calculate the exact iron concentration of each working stan

Question 4 & 5
4. ( Why is the reagent blank necessary? 5. (9 The reaction Fe2+ 2H20-Fe(OH)2 + H occurs readily. Why would this be a problem
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Answer 4- blank reagent means a solution having all component as sample solution except the analyte to be determined. The compounds in the solution may have the impurity of the analyte to be determined and may absorb the radiation of same wavelength. Most of time blank reagent is used to caliberate the instrument to ensure that the measurement device gives a zero signal when there is no sample present so signal of blank can be substracted to get the signal of desired analyte

Answer 5- Fe2+ + 2H2O = Fe(OH)2 + H+ This reaction would be a problem in determination of Iron because of the absence of charge transfer specially Ligand metal charge transfer as in case of iron-phenanthroline complex. Due to absence of charge transfer and d-d transfer Fe(OH)2 is colourless and can not be determined under photospectroscopy technique and exact amount of Fe can not be determined. This can be prevented by maintaining a pH of 2-3. According to le chatelier principle more H+ concentration shifts this reaction towards back.

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