Senior Inter Chemistry Questions and Answers
1. What is the role of cryolite in the extraction of aluminium?
★ To dissolve alumina.
★ To increase electrical conductivity.
★ To decrease the melting point of alumina.
2. How do you distinguish between crystal lattice and unit cell?
Crystal lattice: Regular three dimentional arrangement of points in space.
Unit Cell: The smallest basic three dimentional repeating unit from which crystal lattice is built.
3. What is PHBV? How is it useful to man?
Ans: PHBV is poly β – Hydroxy butyrate Co – β Hydroxy valerate. It is a copolymer, formed due to condensation of 3 – hydroxy butanoic acid and 3 – hydroxy pentanoic acid. This biodegradable polymer is used for making capsules and orthopaedic devices.
4. What are “Frenkel defects” in crystalline solids?
Ans: The stoichiometric, point defect that arises when cation occupies interstitial site instead of lattice sites in crystalline solids.
e.g.: AgCl , AgBr.
5. What is “misch metal”? Give its composition and one use.
Ans: Misch metal is an alloy of 95% Lanthanoid metal and 5% Iron and traces of S, Ca, C and Al. It is used to make bullets.
6. Explain the difference between Buna – N and Buna – S?
Buna – N: Copolymer of 1, 3 Butadiene & Acrylonitrile.
Buna – S: Copolymer of 1, 3 Butadiene and Styrene.
7. What are ‘Elastomers” and “Fibres”?
Elastomers: Polymers in which the inter molecular forces of attraction between the polymer chains are weakest.
e.g.: Buna – S, Buna – N.
Fibres: Polymers in which the intermolecular forces of attraction between the polymer chains are strongest due to Hydrogen bonding (or dipole – dipole interaction).
e.g.: Polyester, Nylon 6, 6.
8. What are “Antacids”? Give 2 examples.
Ans: The chemical substances that removes excess of acid by neutralisation by bringing pH to the normal level in stomach is called “Antacid”.
e.g.: Omeprazole, Lansoprazole.
9. What are “matte” and “Blister Copper”?
Ans: The molten liquid obtained in reverberatory furnace contains mainly Cu2S and little FeS is called “matte”. The solidified Cu obtained in Bessemer converter having blisters (due to evolution of SO2) is called “blister copper”.
10. Write short notes on
a) Analgesics and b) Food preservatives
a) Analgesics: The drugs which are used to reduce or relieve pain without disturbing nervous system. There are 2 types of analgesies:
i) Narcotic analgesies: Analgesies having addictive property, that cause depression of central nervous system and relieves strong pains like cardiac pain and post operative pains.
e.g: Heroin, Morphine.
ii) Non-Narcotic Analgesics: Analgesics having no addictive property and relieves mild aches like head ache, back ache etc.
e.g.: Aspirin, Ibuprofen.
b) Food Preservatives: Chemicals which are added to preserve food by preventing spoilage of food due to microorganisms, to enhance appeal and to increase the nutritive value.
e.g.: Common Salt, Sugar, Sodium Benzoate.
11. What are “F centers”?
Ans: The anion vacancies are occupied by the electrons in metal excess defect. These electrons are responsible for colour and paramagnetic nature.
12. What are “antibiotics”? Give 2 examples.
Ans: Antibiotic is the substance produced by chemical synthesis, which inhibits the growth or destroys disease causing microorganisms. Antibiotics either kill bacteria (bactericidal e.g.: Pencillin, Ofloxacin) or inhibit bacteria (bacterio-static e.g.: erythromycin, Tetracycline).
13. What are “antihistamines”? Give 2 examples.
Ans: The drug that prevents the interaction of histamine with the receptors of stomach wall are called “antihistamines”.
e.g.: Seldane, Dimetane.
14. What are “artificial sweetening agents? Why do we require them?
Ans: The chemical substances not only controls the intake of calories but also gives sweet taste are called artificial sweetening agents.
e.g.: Sucralose, Saccharin.
15. What are “Enantiomers”?
Ans: A pair of stereoisomers having non – super impossible mirror images are called “Enantiomers”.
e.g.: (+) lactic acid & ( – ) lactic acid.
16. Write any four characteristic properties of transition elements.
★ They form alloys readily, due to similar atomic radii (differ not more than 15%).
★ They form coloured compounds due to presence of incomplete d – subshell and d – d transition.
★ They exhibit variable oxidation states as both (n – 1)d and ns electrons take part in bonding (due to little difference in the energies of these orbitals).
★ They form complex compounds due to smaller atomic size, high ionic charge and vailability of vacant d – orbitals.
17. What is Lanthanoid contraction? What are consequences of Lanthanoid contraction?
Ans: The gradual decreage in atomic radii & ionic radii of 14 Lanthanoid elements (with increasing atomic number) due to poor shielding of valence electrons and diffused shape of f orbitals is called “Lathanoid contraction”.
★ Similarity of 4d & 5d elements. ( e.g.: Zr & Hf)
★ Difficulty in separation of Lanthanoides from their mixture due to similar chemical properties and crystal structure.