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CHAPTER

HYDROCARBONS

1. Acetylenic hydrogens are acidic because

[1989] (a) Sigma electron density of C– Hbond in acetylene is nearer to carbon, which has 50% s-character (b) Acetylene has only open hydrogen in each carbon (c) Acetylene contains least number of hydrogens among the possible hydrocarbons having two carbons (d) Acetylene belongs to the class of alkynes with molecular formula, CnH2n – Ans: (a) 2.

[1989] (a) Bromine in carbon tetrachloride (b) Bromine in acetic acid (c) Alk KMnO4 (d) Ammonical silver nitrate. Ans: (d) 3. Select the true statement about benzene

amongst the following [1989] (a) Because of unsaturation benzene easily undergoes addition (b) There are two types of C– Cbonds in benzene molecule (c) There is cyclic delocalisation of pi-electrons in benzene (d) Monosubstitution of benzene gives three isomeric products. Ans: (c) 4.

[1992]

(a) Na (b) HCl in H2O (c) KOH in C2H5OH (d) Zn in alcohol. Ans: (c) 5. Reduction of 2-butyne with sodium in liquid ammonia gives predominantly: [1993] (a) cis - 2 - Butene (b) No reaction (c) trans - 2 - Butene (d) n-Butane. Ans: (c) 6. Acompound is treated with NaNH2 to give sodium salt. Identify the compound [1993] (a) C2H2 (b) C6H6 (c) C2H6 (d) C2H4. Ans: (a) 7. Reactivity of hydrogen atoms attached to different carbon atoms in alkanes has the order [1993] (a) Tertiary > Primary > Secondary (b) Primary > Secondary > Tertiary (c) Both (d) Tertiary > Secondary > Primary Ans: (d) 8. When hydrochloric acid gas is treated with propene in presence of benzoyl peroxide, it gives [1993] (a) 2-Chloropropane (b) Allyl chloride (c) No reaction (d) n-Propyl chloride. Ans: (a) 9. Which of the following compounds has the lowest boiling point? [1994] (a) CH3CH2CH2CH2CH3 (b) CH3CH= CHCH2CH3 (c) CH3CH= CH– CH= CH2 (d) CH3CH2CH2CH3 Ans: (d)

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10. When CH3Cl and AlCl3 are used in Friedel-

Crafts reaction, the electrophile is [1994] (a) Cl+ (b) AlCl4 – (c) CH3+ (d) AlCl2+ Ans: (c) 11. In the free radical chlorination of methane, the chain initiating step involves the formation of [1994] (a) Chlorine free radical (b) Hydrogen chloride (c) Methyl radical (d) Chloromethyl radical. Ans: (a) 12. The alkene R– CH= CH2 reacts readily with B2H6 and formed the product Bwhich on oxidation with alkaline hydrogen peroxides produces [1995]

(a)

(b)

(c)

(d) Ans: (b) 13. When 3, 3-dimethyl 2-butanol is heated with H2 SO4, the major product obtained is [1995] (a) 2,3-dimethyl 2-butene (b) 3, 3-dimethyl 1- butene (c) 2, 3-dimethyl 1- butene (d) cis & trans isomers of 2, 3-dimethyl 2-butene Ans: (a) 14. In the presence of platinum catalyst, hydrocarbon Aadds hydrogen to form n-hexane. When hydrogen bromide is added to Ainstead of hydrogen, only a single bromo compound is formed. Which of the following is A? [1996] (a) CH3 — CH2 — CH = CH— CH2 — CH3 (b) CH3 — CH2 — CH2 — CH = CH— CH3 (c) CH3 — CH = CH— CH2 — CH2 — CH3 (d) CH2 = CH— CH2 — CH2 — CH2 — CH3 Ans: (a) 15.

[1997] (a) CH3CH2Cl and NaOH (b) CH3CH2OHand H2 SO4 (c) CH2Cl – CH2OH and aqueous NaHCO3

(d) Ans: (c) 16. Which one of the following reactions is expected to readily give a hydrocarbon product in good yields? [1997]

(a)

(b)

(c)

(d) Ans: (a) 17. In commercial gasolines the type of hydrocarbons which are more desirable, is [1997] (a) branched hydrocarbons (b) straight-chain hydrocarbons (c) aromatic hydrocarbons such as toluene (d) linear unsaturated hydrocarbons Ans: (a) 18. Ahydrocarbon Aon chlorination gives Bwhich on heating with alcoholic potassium hydroxide changes into another hydrocarbon C. The latter decolourises Baeyer's reagent and on ozonolysis forms formaldehyde only. Ais [1998] (a) Ethane (b) Butane (c) Methane (d) Ethene Ans: (a) 19. The reaction of ethyl magnesium bromide with water would give [1999] (a) Ethane (b) Ethyl alcohol (c) Ethyl bromide (d) Ethyl ether Ans: (a)

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20. Which of the following reagents convert

propene to 1-propanol? [2000] (a) H2O, H2 SO4 (b) aqueous KOH (c) MgSO4, NaBH4 /H2O (d) B2H6, H2O2, OH– Ans: (d) 21. For the formation of toluene by Friedal Craft reaction, reactants used in presence of

anhydrous AlCl3 are [2000] (a) C2H2 and CCl4 (b) CH4 and CaCN2 (c) C6H6 and CH3Cl (d) C2H5 OH and Zn Ans: (c) 22. In preparation of alkene from alcohol using

Al2O3 which is effective factor? [2001] (a) Temperature (b) Concentration (c) Surface area of Al2O3 (d) Porosity of Al2O3 Ans: (a) 23.

[2001]

(a)

(b)

(c)

(d) Ans: (a) 24.

[2003] (a) CH3CHO+ CO2

(b) CH3COCH3 (c) CH3COCH3 + CH3COOH (d) CH3COCH3 + CH3CHO Ans: (c) 25. Reaction of HBr with propene in the

presence of peroxide gives [2004] (a) isopropyl bromide (b) 3-bromo propane (c) allyl bromide (d) n-propyl bromide Ans: (d) 26. Using anhydrous AlCl3 as catalyst, which one of the following reactions produces

ethylbenzene (PhEt) ? [2004]

(a)

(b)

(c)

(d) Ans: (c) 27. Which one of the following alkenes will react faster with H2 under catalytic hydrogenation

conditions? (R= Alkyl Substituent) [2005]

(a)

(b)

(c)

(d) Ans: (a) 28.

[2005] (a)

(b)

(c)

(d)

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Ans: (b) 29.

[2007]

(a)

(b)

(c)

(d) Ans: (c) 30. Which of the compounds with molecular formula C5H10 yields acetone on ozonolysis?

[2007] (a) 3-methyl-1-butene (b) cyclopentane (c) 2-methyl-1-butene (d) 2-methyl-2-butene. Ans: (d) 31.

[2008]

(a)

(b)

(c)

(d) Ans: (b)

32.

[2009] (a) 1-butyn-3-ene (b) but-1-yne-3-ene (c) 1-butene-3-yne (d) 3-butene-1-yne Ans: (c) 33. Liquid hydrocarbons can be converted to a

mixture of gaseous hydrocarbons by: [2010] (a) Oxidation (b) Cracking (c) Distillation under reduced pressure (d) Hydrolysis Ans: (b) 34.

[2010] (a)

(b)

(c)

(d) Ans: (d) 35. The IUPACname of the compound CH3CH=

CHC= CH is [2010] (a) Pent-l-yn-3-ene (b) Pent-4-yn-2-ene (c) Pent-3-en-1-yne (d) Pent-2-en-4-yne Ans: (c) 36.

[2011]

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(a)

(b)

(c)

(d) Ans: (b) 37.

[2012]

(a)

(b)

(c)

(d) Ans: (a) 38. Which of the following reagents will be able to distinguish between 1-butyne and 2-butyne?

[2012] (a) NaNH2 (b) HCl (c) O2 (d) Br2 Ans: (a) 39.

[2013] (a) 7 p-orbitals and 6 unpaired electrons (b) 7 p-orbitals and 7 unpaired electrons (c) 6 p-orbitals and 7 unpaired electrons (d) 6 p-orbitals and 6 unpaired electrons Ans: (d) 40.

[2013] (a) Iodoform test (b) Tollen’s reagent test (c) Brady’s reagent test (d) Victor Meyer test Ans: (d) 41. Which of the following chemical system is

non aromatic? [2013]

(a)

(b)

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(c)

(d) Ans: (a) 1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

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13.

14.

15.

16.

17.

18.

19.

20.

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21.

22.

23.

24.

25.

26.

27.

28.

29.

30.

Chapterwise Previous year Qs

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31. 32. 33. 34. 35. 36. 37. 38.

39.

40.

41.