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प्रश्न
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with iodide.
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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)
The iodide ion (I−) is oxidised to I2 by the acidified solution of K2Cr2O7.
\[\ce{Cr2O^2-_7 + 14H+ + 6e- -> 2Cr^{3+} + 7H2O}\]
\[\ce{6I- -> 3I2 + 6e-}\]
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\[\ce{Cr2O^2-_7 + 14H+ + 6I- -> 2Cr^{3+} + 7H2O + 3I2\uparrow}\]
संबंधित प्रश्न
How is the variability in oxidation states of transition metals different from that of the non-transition metals? Illustrate with examples.
Compare the general characteristics of the first series of the transition metals with those of the second and third series metals in the respective vertical columns. Give special emphasis on the following point:
Electronic configurations
Generally transition elements form coloured salts due to the presence of unpaired electrons. Which of the following compounds will be coloured in solid-state?
Ionisation enthalpies of Ce, Pr and Nd are higher than Th, Pa and U. Why?
While filling up of electrons in the atomic orbitals, the 4s orbital is filled before the 3d orbital but reverse happens during the ionisation of the atom. Explain why?
Assertion (A): Cu cannot liberate hydrogen from acids.
Reason (R): Because it has positive electrode potential.
Identify the metal and justify your answer.
Carbonyl \[\ce{M(CO)5}\]
A violet compound of manganese (A) decomposes on heating to liberate oxygen and compounds (B) and (C) of manganese are formed. Compound (C) reacts with KOH in the presence of potassium nitrate to give compound (B). On heating compound (C) with conc. \[\ce{H2SO4}\] and \[\ce{NaCl}\], chlorine gas is liberated and a compound (D) of manganese along with other products is formed. Identify compounds A to D and also explain the reactions involved.
Fill in the blanks by choosing the appropriate word(s) from those given in the brackets:
(activation energy, Threshold energy, increased, lowered, partially, full, d-d transition, Benzoic acid, benzaldehyde)
Only those transition metal ions will be coloured which have ______ filled d-orbitals facilitating ______.
Which of the following is non-metallic?
Mercury is the only metal liquid at room temperature due to its:-
Among the following pairs of ions, the lower oxidation state in aqueous solution is more stable than the other in:-
The basic character of transition metals monoxide follow the order.
Which of the following ions will exhibit colour in aqueous solution?
Why Zn, Cd and Hg are not called transition metals?
Which of the following transition metals shows +1 and +2 oxidation states?
Write the number of unpaired electrons in Cr3+.
(Atomic number of Cr = 24)
Explain the use of different transition metals as catalysts.
A coordination compound has the formula \[\ce{CoCl3.4NH3}\]. It precipitates silver ions as AgCl and its molar conductance corresponds to a total of two ions.
Based on this information, answer the following question:
- Deduce the structural formula of the complex compound.
- Write the IUPAC name of the complex compound.
- Draw the geometrical isomers of the complex compound.
