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Question
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with iodide.
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Solution
Potassium dichromate acts as a strong oxidizing agent. It is used as a primary standard in volumetric analysis. The oxidation action of dichromate ion in an acidic medium can be represented as follows:
\[\ce{Cr2O^2-_7 + 14H+ + 6e^- -> 2Cr^{3+} + 7H2O}\] (E– = 1.33 V)
The iodide ion (I−) is oxidised to I2 by the acidified solution of K2Cr2O7.
\[\ce{Cr2O^2-_7 + 14H+ + 6e- -> 2Cr^{3+} + 7H2O}\]
\[\ce{6I- -> 3I2 + 6e-}\]
______________________________________________
\[\ce{Cr2O^2-_7 + 14H+ + 6I- -> 2Cr^{3+} + 7H2O + 3I2\uparrow}\]
RELATED QUESTIONS
Which metal in the first transition series (3d series) exhibits + 1 oxidation state most frequently and why?
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| (i) \[\ce{Ni}\] in the presence of hydrogen | (a) Zieglar Natta catalyst |
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| (v) \[\ce{TiCl4 + Al (CH3)3}\] | (e) Haber's Process |
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