Chemistry

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1
in vapour state sulphur partly exists as S2 molecule which has 2 unpaired electrons in the antibondind pi orbitals jus lyk oxygen and thus exhibits paramagnetism.

2
An interhalogen compound is a molecule whose atom contains two or more different halogen atoms (fluorine, chlorine, bromine, iodine or astatine).

Most interhalogen compounds known are binary (composed of only two distinct elements). Their formulas are generally XYn, where n = 1, 3, 5 or 7, and X is the less electronegative of the two halogens. They are all prone to hydrolysis, and ionise to give rise to polyhalogen ions.

No interhalogen compounds containing three or more different halogens are known[1], although a couple of books claim that IFCl2 and IF2Cl have been obtained,[2][3][4][5] and theoretical studies seem to indicate that some compounds in the series BrClFn are barely stable.[6]

3
A nitrate test is a chemical test used to determine the presence of nitrate ion in solution.

A common nitrate test, known as the brown ring test[1] can be performed by adding iron(II) sulfate to the solution, then slowly adding concentrated sulfuric acid (NOT nitric acid, for obvious reasons) and watching for a brown ring on the test tube, which will indicate the presence of the nitrate ion.[2] Note that the presence of nitrite ions will interfere with this test.[3]

The test follows several phases; these have been written as balanced chemical equations:

1: 2 Zn(NO3)2 + 2 H2SO4 ? 2 ZnSO4 + 4 HNO3

4 FeSO4 + 2 H2SO4 ? 2 Fe2(SO4)3 + H2

These two reactions happen simultaneously.

2: 4 HNO3 ? 2 H2O + 3O2 + 2 NO

The Nitric Acid decomposes in the intense heat produced by the high concentrate Sulphuric Acid used.

3: 2 Fe2(SO4)3 + 2 H2 + 4 NO ? 4 Fe.NO.SO4 + 2 H2SO4

The Fe.NO.SO4 forms a brown ring in the middle of the solution produced by the reaction, making it easy to identify the presence of nitrates in the water.

4.
LABORATORY METHOD

In laboratory Cl2 gas is prepared by heating a mixture of NaCl , MnO2 with conc. H2SO4. 4NaCl +4H2SO4 +MnO2è 4NaHSO4 +MnCl2+2H2O +Cl2

OVERALL REACTION

2Na+ + 2H2O + 2e-è 2NaOH + H2
2Cl-è Cl2+ 2e-
--------------------------------------
2Na+ 2Cl- + 2H2Oè 2NaOH + Cl2 +H2

5.
Using a filter paper that is dampened with potasium dichromate. The paper will change from orange to green as SO2 reduces Cr2O7 2-(orange) ion to the Cr3+(green).

N.B. SO2 is a reducing agent

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Zn (s) + HNO3 (aq) --> H2 (g) + Zn(NO3)2 (aq)

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Nickel is purified by Mond's process.
It is first reacted with Carbon Monoxide to form a volatile complex i.e Ni(CO)4 . Then the carbonyl is subjected to higher temperature so that it is decomposed to give pure Nickel.

Ni(CO)4 -----------> Ni + 4CO

8.

generally speaking, copper and many other base metals are processed in a very similar fashion. The raw ore is crushed into small bits and processed to concentrate the metal minerals. This is called density separation; metal ore minerals tend to be of much higher density than the gangue (the non-value minerals). There are also chemical ways of producing a concentrate of ore minerals

The "concentrate" is then sent to a smelter where it is melted. Since most metal ores see the metal in minerals under an oxidized form (as a cation), the metal must be reduced. Commonly this is done in the presence of carbon, the carbon reduces the metal cation to the neutral elemental form (the carbon is oxidized in its turn to CO2). Reduction by carbon means that the metal gets electrons from the carbon, changing the metal's charge state from positive to neutral.

During smelting, a very rich metal product is formed that can be separated physically (usually as a liquid) from the gangue residues, which are now called slag (waste rock from smelting).

Many metals, copper among them, also undergo an additional step of purification involving electricity. The raw ore, which is fairly pure but not super pure, is...
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