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Random Questions in Objective Chemistry
Name the following:
1. The most radio active alkali metal
2. An Organic liquid which bursts into flames on addition of conc. nitric acid.
3. A metallic sulphide soluble in water
4. An explosive formed when ammonia reacts with excess of chlorine
5. A gas having a pungent choking smell, used to bleach fruit juices
6. An unsaturated hydrocarbon formed by dehydration of ethyly alcohol with concentrated sulphuric acid
7. A coloured metallic hydroxide insoluble in excess of sodium hydroxide but soluble in excess of ammonium hydroxide
8. A salt which decomposes on heating to give a metal as residue
9. An insoluble salt formed from two soluble salt solutions, one of which is sodium chloride solution
10.A metalic sulphide insoluble in water.
11. The colour of Xanthoproteic acid
12. A nitrate which leaves a black residue on heating
13. The compound also known as chile salt petre
14. The catalyst used for conversion of sulphur dioxide to sulphur trioxide
15. A substance used to absorb arsenic impurity
Give reasons for the following:
1. Large quantities of sulphuric acid are used in iron and steel industry.
2. All glass apparatus should be used in preparing nitric acid by heating conc. sulphuric acid and potassium nitrate.
3. Lime juice has a sour taste but lime water is bitter.
4. During electroplating, a small current current should be used for a longer time.
5. Aluminium is extracted from its oxide by electrolytic reduction and not by conventional reducing agents.
6. Ammonia is unionised in the gaseous state but in the aqueous solution is a weak electrolyte.
7. Carbon tetrachloride is liquid but does not conduct electricity.
8. Why is it necessary to add an acid to water before proceeding with electrolysis of water
9. Aluminium is used in flash bulbs.
10. Non metals are good oxidising agents.
11. The catalyst chamber in the formation of ammonia provided with ammonia exchanger
12. Ammonia is present in sewage water.
13. Ammonia is used as a cleansing agent
14. Commercial concentrated nitric acid is yellow, but turns colorless when diluted with water.
15. In the laboratory preparation of nitric acid, the mixture of concentrated sulphuric acid and sodium nitrate should not be heated above 200 degrees centigrade.
Name a metal which:
1. is a liquid at room temperature -
2. is so soft that it can be cut with a knife.-
3. is a bad conductor of heat
4. is store in kerosene-
5. is brittle-
2. turpentine oil
3. sodium sulphide
4. nitrogen trichloride
5. sulphur dioxide
7. copper hydroxide
8. silver nitrate
9. lead chloride
10. zinc sulphide
12. Copper Nitrate
13. Sodium Nitrate
14. Vanadium Pentaoxide
15. Ferric Hydroxide
1. Large quantities of sulphuric acid are used in iron and steel industry to remove the coating of oxide from the surface of iron or steel before metal is plated, or before it is coated with an enamel.
2. All glass apparatus should be used in preparing nitric acid by heating conc. sulphuric acid and potassium nitrate because nitric acid produced reacts with almost all the materials including cork and rubber. It does not react with glass.
4.During electroplating, a small current current should be used for a longer time because the thickness of the coating depends on the time for which it the current is passed.
5. This is because aluminium is a good reducing agent and has a great affinity for oxygen, and can’t be reduced by reducing agents.
6. Ammonia is a covalent compound. Therefore it is unionised in the gaseous state but in the aqueous solution it gives NH4OH which dissociates slightly.
7. Because it is a covalent compound and there are no free ions present.
8. It is necessary to add an acid to water before proceeding with electrolysis of water because pure water is a poor conductor of electricity. Acid is added to make it a good conductor.
9.Aluminium is used in flash bulbs because aluminium burns in oxygen to produce intense white light.
10. because they gain electrons.
11.The catalyst chamber in the formation of ammonia is provided with ammonia exchanger so that the outgoing ammonia gas and the unreacted gases exchange their heat with the incoming nitrogen and hydrogen.
12. Ammonia is present in sewage water beacuse it is produced due to bacterial decomposition of urea present in urine.
13. Ammonia is used as a cleansing agent. Ammonia is used for removing grease and perspiration stains from clothers, windows etc. because ammonia solution emulsifies fats and grease, i.e. breaks down the fat and grease molecules so that they can be removed without leaving any residue.
14. Commercial concentrated nitric acid is yellow due to the presence of dissolved nitrogen dioxide in it, but turns colorless when diluted with water because nitrogen dioxide dissolves in water to form nitric acid which is colourless..
15. In the laboratory preparation of nitric acid, the mixture of concentrated sulphuric acid and sodium nitrate should not be heated above 200 degrees centigrade because of the following reasons:
i) the sodium sulphate formed at higher temperatures forms a hard crust which sticks to the walls of the retort and is difficult to remove.
ii) the glass apparatus may crack at higher temperature.
iii) the decomposition of nitric acid occurs to a great extent at higher temperatures thereby imparting brown colour to nitric acid.