Why is it necessary to carry out the reduction of iron and then the titration, before going on to the next sample 5. If you look carefully, there are pieces of tin metal on the bottom of the SnCl2 reagent solution. Why is it there?

Fundamentals Of Analytical Chemistry
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ISBN:9781285640686
Author:Skoog
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Chapter17: Complexation And Precipitation Reactions And Titrations
Section: Chapter Questions
Problem 17.35QAP
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For Redox Analysis of Iron...

~0.02 M of potassium dichromate is prepared as titrant for dried unknown.

~.3 g of sample, 50ml of 6M HCl, 20mL SnCl2, 10 mL of saturated HgCl2 solution, 60 mL of 3M H2SO4, 15mL of concentrated H3PO4, 100mL DI water.

HCl (+ heat in fumehood until samples dissolves), SnCl2 (added with pipet until solution changes from yellow to colorless/light green with 3 drops in excess), HgCl2 (after cooling), H2SO4, H3PO4, DI Water, is added to the sample solution with 8 drops of diphenylamine sulfonate indicator then titrated with the potassium dichromate to a violet blue endpoint.

4. Why is it necessary to carry out the reduction of iron and then the titration, before going on to the next sample

5. If you look carefully, there are pieces of tin metal on the bottom of the SnCl2 reagent solution. Why is it there?

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