Advertisements
Advertisements
Question
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with iodide.
Advertisements
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
The elements of 3d transition series are given as: Sc Ti V Cr Mn Fe Co
Answer the following: Write the element which shows maximum number of oxidation states. Give reason.
What are the transition elements? Write two characteristics of the transition elements.
Account for the following:
Cu+ ion is unstable in aqueous solution.
Account for the following:
E° value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+.
Compare the stability of +2 oxidation state for the elements of the first transition series.
Write the factors which are related to the colour of transition metal ions.
Explain why transition metals and their compounds act as a catalyst.
Give reasons for the following:
The transition metals generally form coloured compounds.
Transition metals with lowest melting point is ______.
Generally transition elements form coloured salts due to the presence of unpaired electrons. Which of the following compounds will be coloured in solid-state?
When \[\ce{KMnO4}\] solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because ______.
\[\ce{KMnO4}\] acts as an oxidising agent in acidic medium. The number of moles of \[\ce{KMnO4}\] that will be needed to react with one mole of sulphide ions in acidic solution is ______.
Interstitial compounds are formed when small atoms are trapped inside the crystal lattice of metals. Which of the following is not the characteristic property of interstitial compounds?
When an oxide of manganese (A) is fused with KOH in the presence of an oxidising agent and dissolved in water, it gives a dark green solution of compound (B). Compound (B) disproportionates in neutral or acidic solution to give purple compound (C). An alkaline solution of compound (C) oxidises potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and also explain the reactions involved.
Which of the following species has maximum magnetic momentum?
On adding NaOH, solution to the aqueous solution of K2CrO7 the colour of the solution changes from
Which of the following ions acts as a typical transition metal ion?
Give two similarities in the properties of Sc and Zn.
Give a reason for the following:
Zinc, cadmium and mercury are considered as d-block elements but not regarded as transition elements.
