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प्रश्न
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.
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उत्तर
The compounds A, B, C and D are given as under:
A = \[\ce{KMnO4}\]
B = \[\ce{K2MnO4}\]
C = \[\ce{MnO2}\]
D = \[\ce{MnCl2}\]
The reactions are explained as under:
\[\ce{\underset{(A)}{KMnO4} ->[Δ] \underset{(B)}{K2MnO4} + \underset{(C)}{MnO2} + O2}\]
\[\ce{MnO2 + KOH + O2 -> 2K2MnO4 + 2H2O}\]
\[\ce{MnO2 + 4NaCl + 4H2SO4 -> \underset{(D)}{MnCl2} + 2NaHSO4 + 2H2O + Cl2}\]
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संबंधित प्रश्न
In what way is the electronic configuration of the transition elements different from that of the non-transition elements?
How would you account for the following:
Cobalt (II) is stable in aqueous solutions, but in the presence of complexing reagents, it is easily oxidised.
NF3 is possible, but NF5 is not. Why?
How would you account for the following?
Transition metals and their compounds act as catalysts.
An analysis shows that FeO has a non-stoichiometric composition with formula Fe0.95O. Give reason.
Give reasons:
E° value for the Mn3+/Mn2+ couple is much more positive than that for Fe3+/Fe2+.
Give reasons for the following:
The transition metals generally form coloured compounds.
Read the passage given below and answer the following question:
The transition metals when exposed to oxygen at low and intermediate temperatures form thin, protective oxide films of up to some thousands of Angstroms in thickness. Transition metal oxides lie between the extremes of ionic and covalent binary compounds formed by elements from the left or right side of the periodic table. They range from metallic to semiconducting and deviate by both large and small degrees from stoichiometry. Since electron bonding levels are involved, the cations exist in various valence states and hence give rise to a large number of oxides. The crystal structures are often classified by considering a cubic or hexagonal close-packed lattice of one set of ions with the other set of ions filling the octahedral or tetrahedral interstices. The actual oxide structures, however, generally show departures from such regular arrays due in part to distortions caused by packing of ions of different size and to ligand field effects. These distortions depend not only on the number of d-electrons but also on the valence and the position of the transition metal in a period or group.
In the following questions, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices on the basis of the above passage.
Assertion: Transition metals form protective oxide films.
Reason: Oxides of transition metals are always stoichiometric.
Reactivity of transition elements decreases almost regularly from Sc to Cu. Explain.
Match the solutions given in Column I and the colours given in Column II.
| Column I (Aqueous solution of salt) |
Column II (Colour) |
| (i) \[\ce{FeSO2.7H2O}\] | (a) Green |
| (ii) \[\ce{NiCl2.4H2O}\] | (b) Light pink |
| (iii) \[\ce{MnCl2.4H2O}\] | (c) Blue |
| (iv) \[\ce{CoC12,6H2O}\] | (d) Pale green |
| (v) \[\ce{Cu2 Cl2}\] | (e) Pink |
| (f) Colourless |
Assertion: The highest oxidation state of osmium is +8.
Reason: Osmium is a 5d-block element.
Why are fluorides of transition metals more stable in their higher oxidation state as compared to the lower oxidation state?
The product of oxidation of I– with \[\ce{MnO^{-}4}\] in alkaline medium is:-
On adding NaOH, solution to the aqueous solution of K2CrO7 the colour of the solution changes from
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`]
Write the number of unpaired electrons in Cr3+.
(Atomic number of Cr = 24)
Describe the oxidising action of potassium dichromate and write the ionic equation for its reaction with H2S.
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:
Oxidation states
Match List-I with List-II.
| List-I | List-II |
| A. Haber process | I. Fe catalyst |
| B. Wacker oxidation | II. PdCl2 |
| C. Wilkinson catalyst | III. [(PPh3)3RhCl] |
| D. Ziegler catalyst | IV. TiCl4 with Al(CH3)3 |
Choose the correct answer from the options given below:
The E° value for the Mn2+/Mn2+ couple is more positive than that of Cr3+/Cr2+ or Fe3+/Fe2+ due to the change of:
