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Give one example each of 'oil in water' and 'water in oil' emulsion.
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Type of emulsion |
Example |
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Oil in water |
Milk, vanishing cream |
|
Water in oil |
Butter, cold cream, cod liver oil |
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Which reducing agent is employed to get copper from the leached low-grade copper ore?
Copper can be obtained from low-grade ore through the process of leaching using acid or bacteria (leaching is a process in which ore is treated with a suitable reagent that dissolves ore but not the impurities).
The solution containing copper can be reduced with the help of reducing agents such as scrap iron or H2 to get copper metal.
Cu2+(aq) + Fe Cu(s) + Fe2+(aq)
Cu2+ (aq) + H2(g) Cu(s) + 2 H+(aq)
Which of the following is a more stable complex and why?
(i) [Co(NH3)6]3+
(ii) [Co(en)3]3+
Chelating ligands form more stable complexes compared to non-chelating ligands. Since ethylene diamine is a bidentate ligand and forms stable chelate, [Co(en)3]3+ will be a more stable complex than [Co(NH3)6]3+
An element with density 11.2 g cm-3 forms a f.c.c. lattice with edge length of 4 x10-8
Calculate the atomic mass of the element. (Given: NA = 6.022x 10-23 (mol-1)
Density, d = 11.2 g cm-3
Edge length, a = 4x10-8 cm
Avogadro number, NA = 6.022x1023 mol-1
Number of atoms present per unit cell, Z (fcc) = 4
We know for a crystal system,
Thus, the atomic mass of the element is 107.91 g.
Examine the given defective crystal:
Answer the following questions:
(i) What type of stoichiometric defect is shown by the crystal?
(ii) How is the density of the crystal affected by this defect?
(iii) What type of ionic substances shows such defect?
(i) Schottky defect is shown by the mentioned crystal, as an equal number of cations and anions are missing in the crystal lattice.
(ii) This defect leads to decrease in density, as an equal number of the cations and anions are missing from the crystal lattice. A number of such defects in ionic solids are quite significant. For example, in NaCl, there are approximately 106 Schottky pairs per cm3 at room temperature.
(iii) This kind of defect is shown by that ionic substance in which the cations and anions are of almost similar sizes.
Examples: NaCl, KCl and CsCl.
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