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प्रश्न
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with H2S.
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उत्तर
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)
H2S is oxidised to sulphur.
\[\ce{Cr2O^2-_7 + 8H^+ + 3H2S -> 2Cr^3+ + 7H2O + 3S}\]
संबंधित प्रश्न
Account for the following:
Cr2+ is a strong reducing agent.
Why is the highest oxidation state of a metal exhibited in its oxide or fluoride only?
What are inner transition elements?
Write the factors which are related to the colour of transition metal ions.
Dissociation of H2S is suppressed in acidic medium.
Two metallic elements A and B have the following standard oxidation potentials: A = 0·40v B = - 0·80v. What would you expect if element A was added to an aqueous salt solution of element B? Give a reason for your answer.
Explain why transition elements form alloys.
Explain why transition metals and their compounds act as a catalyst.
When \[\ce{KMnO4}\] solution is added to oxalic acid solution, the decolourisation is slow in the beginning but becomes instantaneous after some time because ______.
Which of the following will not act as oxidising agents?
(i) \[\ce{CrO3}\]
(ii) \[\ce{MoO3}\]
(iii) \[\ce{WO3}\]
(iv) \[\ce{CrO^{2-}4}\]
The second and third rows of transition elements resemble each other much more than they resemble the first row. Explain why?
Assertion: Separation of \[\ce{Zr}\] and \[\ce{Hf}\] is difficult.
Reason: Because \[\ce{Zr}\] and \[\ce{Hf}\] lie in the same group of the periodic table.
When a chromite ore (A) is fused with sodium carbonate in free excess of air and the product is dissolved in water, a yellow solution of compound (B) is obtained. After treatment of this yellow solution with sulphuric acid, compound (C) can be crystallised from the solution. When compound (C) is treated with KCl, orange crystals of compound (D) crystallise out. Identify A to D and also explain the reactions.
The standard electrode potentials of four elements A, B, C and D are – 3.05, – 1.66, – 0.40 and + 0.80. The highest chemical reactivity will be exhibited by
A complex in which dsp2 hybridisation takes place is ______.
Give reason for the following statement:
[Ti(H2O)]3+ is coloured while [Sc(H2O)6]3+ is colourless.
In the ground state of atomic Fe (Z = 26), the spin-only magnetic moment is ______ × 10-1 BM.
(Round off to the nearest integer).
[Given: `sqrt3 = 1.73, sqrt2 = 1.41`]
The oxidation state of Fe in [Fe(CO)5] is ______.
Assertion (A): Transition metals have high enthalpy of atomisation.
Reason (R): Greater number of unpaired electrons in transition metals results in weak metallic bonding.
