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CHEMISTRYCHAPTER-22 (OBJECTIVE)CLASS TEST-1
TIME: 10 MINTOTAL MARKS:30MARKS: 8
1. General formula of alkene is:(Q-2)
(a) CnH2n+2(b) CnH2n✔(c) CnH2n−2(d) H2n+1
2. Dehydration of alcohol can be carried out at temperature:(Q-4)
(a) 120°C(b) 140°C(c) 160°C(d) 180°C✔
3. Hydrogenation of alkene take place in the presence of catalyst is:(Q-7)
(a) H2SO4(b) Zn(c) Alcohol(d) Ni✔
4. Formula of Steam is:(Q-10)
(a) H2SO4(b) H2O✔(c) HBr(d) KmnO4
5. Major sources of organic compounds is:(Q-16)
(a) Coal(b) Petroleum(c) Natural gas(d) All✔
6. After the flow of gases ceases, Petroleum is taken out with the help of:(Q-19)
(a) valves(b) Pumps✔(c) cranes(d) Compressors
7. Crude Petroleum is heated at:(Q-23)
(a) 400°C✔(b) 450°C(c) 500°C(d) 550°C
8. Boiling Range of Fuel oil is:(Q-26)
(a) 170–250(b) 250–340(c) 340–500✔(d) above 500
CHEMISTRYCHAPTER-22 (SUBJECTIVE)CLASS TEST-1
TIME: 22 MINMARKS: 22
Attempt any 7 Questions.7×2=14
i.What is alkene? Give its General Formula.(Q-1)
Ans: Alkenes are unsaturated hydrocarbons that contain a carbon–carbon double bond (C=C) in their molecules. General formula: CnH2n (e.g. ethene C2H4).
ii.Give some uses of alkenes.(Q-3)
Ans: (1) Used to make polythene and other plastics. (2) Used to prepare ethanol and ethylene glycol (antifreeze). (3) Ethene is used for artificial ripening of fruits. (4) Used to prepare many useful organic chemicals and solvents.
iii.How cracking can be carried out?(Q-6)
Ans: Cracking is the breaking of large hydrocarbon molecules into smaller, more useful ones. It is carried out by heating heavy fractions of petroleum at high temperature (thermal cracking) or in the presence of a catalyst such as silica–alumina (catalytic cracking). Example: C10H22 → C5H12 + C5H10
iv.Define addition reaction? Give an example.(Q-9)
Ans: A reaction in which atoms or groups add to the double (or triple) bond of an unsaturated compound, forming a saturated compound, is called an addition reaction. Example (hydrogenation of ethene): CH2=CH2 + H2 →(Ni, 200°C) CH3–CH3
v.Give a test to identified saturated and unsaturated hydrocarbon.(Q-11)
Ans: Bromine water test: shake the hydrocarbon with a few drops of reddish-brown bromine water. An unsaturated hydrocarbon decolourises it; a saturated hydrocarbon does not. (Similarly, unsaturated hydrocarbons decolourise pink KMnO4 solution.)
vi.What is alkynes? Give example.(Q-14)
Ans: Alkynes are unsaturated hydrocarbons containing a carbon–carbon triple bond (C≡C). General formula: CnH2n−2. Example: ethyne (acetylene) HC≡CH
vii.Why use of calcium carbide is prohibited in our country?(Q-18)
Ans: Calcium carbide is used to ripen fruits artificially. It gives ethyne gas containing traces of arsenic and phosphorus compounds, which are harmful to human health, so its use is prohibited.
viii.Where are Petroleum and natural gas found underground?(Q-20)
Ans: They are found trapped between layers of impervious rocks deep under the earth (in porous sedimentary rocks). Natural gas lies on top, petroleum below it, and salt water at the bottom.
ix.Write the uses of Benzene:(Q-22)
Ans: Benzene is used as a solvent, and for making dyes, drugs, detergents, plastics, insecticides and explosives.
x.Write any two steps of refining.(Q-24)
Ans: (1) Removal of water and salts from the crude petroleum. (2) Heating the crude petroleum in a furnace to about 400°C and separating it into fractions by fractional distillation in a fractionating tower.
SECTION-II (4+4)
1.Describe two methods of preparation for ethene.(Ex. D. 22.1)
Ans: (a) Dehydration of ethanol: ethanol is heated with conc. H2SO4 at about 180°C.
C2H5OH →(conc. H2SO4, 180°C) CH2=CH2 + H2O
(b) Dehydrohalogenation of ethyl halide: ethyl chloride is heated with alcoholic KOH.
CH3CH2Cl + KOH(alc.) → CH2=CH2 + KCl + H2O
2.Which properties of petroleum fractions change with their boiling points?(Ex. D. 22.3)
Ans: As the boiling point of a fraction increases: (1) its viscosity (thickness) increases; (2) its colour becomes darker; (3) its volatility and ease of ignition decrease; (4) the number of carbon atoms and the molecular mass increase; (5) it burns with a more smoky flame.
