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प्रश्न
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.
उत्तर
The compounds A, B, C and D are given as under:
A = \[\ce{FeCr2O4}\]
B = \[\ce{Na2CrO4}\]
C = \[\ce{Na2Cr2O7.2H2O}\]
D = \[\ce{K2Cr2O7}\]
The reactions are explained as under:
\[\ce{\underset{(A)}{4FeCr2O4} + 8NaCO3 + 7O2 -> \underset{(B)}{8Na2CrO4} + 2Fe2O3 + 8CO2}\]
\[\ce{2NaCrO4 + 2H^+ -> Na2CrO7 + 2Na^+ + H2O}\]
\[\ce{\underset{(C)}{Na2CrO7} + 2KCl -> \underset{(D)}{K2Cr2O7} + 2NaCl}\]
APPEARS IN
संबंधित प्रश्न
Account for the following:
Mn shows the highest oxidation state of +7 with oxygen but with fluorine, it shows oxidation state of +4.
|
`E_((M^(2+)/M)` |
Cr | Mn | Fe | Co | Ni | Cu |
| -0.91 | -1.18 | -0.44 | -0.28 | -0.25 | -0.34 |
From the given data of E0 values, answer the following questions :
(1) Why is `E_(((Cu^(2+))/(Cu)))` value exceptionally positive
(2) Why is `E_(((Mn^(2+))/(Mn)))` value is highly negative as compared to other elements
(3) Which is the stronger reducing agents Cr2+ or Fe2+ ? Give Reason.
Calculate the ‘spin only’ magnetic moment of \[\ce{M^{2+}_{ (aq)}}\] ion (Z = 27).
The transition metals show _________ character because of the presence of unpaired· electrons and Cu+ is ____________ because of its electronic configuration is [Ar]3d10
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: Cations of transition elements occur in various valence states.
Reason: Large number of oxides of transition elements are possible.
Mercury is the only metal liquid at room temperature due to its:-
Why Zn, Cd and Hg are not called transition metals?
The disproportionation of \[\ce{MnO^{2-}_4}\] in acidic medium resulted in the formation of two manganese compounds A and B. If the oxidation state of Mn in B is smaller than that of A, then the spin-only magnetic moment (µ) value of B in BM is ______. (Nearest integer)
Account for the following:
Ce4+ is a strong oxidising agent.
Write the number of unpaired electrons in Cr3+.
(Atomic number of Cr = 24)
