AL Chemistry Experiment Report Sheet

Experiment 28, 29: Illustrating the Oxidation States of Vanadium and Manganese

Name: ___________________ ( ) Form 7 S

Illustrating the Oxidation States of Vanadium

Test	Observations	Summary of reaction
Ammonium vanadate + acid	White solid dissolved to a yellow solution	VO₃^- ¾® VO₂⁺ + 5 ¾® +5
Vanadium(V) + zinc
Vanadium(II) + manganate(VII)
Vanadium(V) + sulphite Add vanadium(II)
Vanadium(V) + idodide + thiosulphate
Vanadium(II) + _____________

Questions

1. How do you explain the first appearance of a green colour in the solution?

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2. What are the subsequent changes in colour and why do these changes occur?

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3. What did you observe when you added iodide ions to vanadium(V)? What caused this colour?

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4. Why did you add sodium thiosulphate?

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5. Why does reduction with iodide not give the same result as reduction with zinc?

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6. What did you observe when you added sulphite ions to acidified vanadium(V) solution? Does this result correspond with a prediction made using the E^Æ values?

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7. How would you set about finding a suitable oxidizing agent for the oxidation of vanadium(II) to vanadium(III) and no further? Does one appear in the table above?

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Illustrating the Oxidation States of Manganese

1. Explain why only one of the three mixtures reacted to give green Mn(VI).

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2. What happened when acid was added to Mn(VI)? Explain.

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3. Explain why happened when the Mn(III) solution was diluted.

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4. Can you see any sign of Mn(III) in the tubes?

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5. What is different about the conditions of this experiment (Part C) compared with the last (Part B) which makes its success less likely?

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6. What happens in test tube which had no manganese(IV) added? Suggest an explanation. (Hint: is the change greater in the upper part of the mixture?)

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The End