NEET UG - Preparation properties reactions nature of C-X bond mechanisms of substitution and environmental effects of chloroform freons and DDT Online Test (MCQ Quiz)

1. Which of the following is the most common method for the laboratory preparation of Chloroform?

A) Reaction of ethanol with bleaching powder B) Reaction of acetone with bleaching powder C) Reaction of methane with chlorine under UV light D) Hydrolysis of carbon tetrachloride

2. When ethanol reacts with bleaching powder (CaOCl2), what are the primary products formed before the final formation of chloroform?

A) Acetaldehyde and calcium hydroxide B) Acetic acid and calcium chloride C) Ethylene and hypochlorous acid D) Ethanol chloride and calcium oxide

3. The reaction of acetone with bleaching powder yields chloroform through which of the following intermediate steps?

A) Oxidation followed by chlorination and hydrolysis B) Chlorination followed by oxidation and hydrolysis C) Hydrolysis followed by chlorination and oxidation D) Direct substitution of hydrogen by chlorine

4. What is the chemical formula for Chloroform?

A) CCl4 B) CH3Cl C) CHCl3 D) CH2Cl2

5. Which of the following conditions is essential for the free radical chlorination of methane to produce chloroform?

A) Presence of a catalyst like FeCl3 B) High pressure C) Presence of UV light or visible light D) Absence of oxygen

6. What is the characteristic smell of chloroform?

A) Sweetish B) Pungent C) Earthy D) Pleasant

7. Chloroform is:

A) Slightly soluble in water B) Insoluble in water C) Miscible with water D) Reacts with water to form HCl

8. Chloroform is readily soluble in:

A) Water B) Dilute acids C) Organic solvents like ether and alcohol D) Dilute bases

9. When chloroform is heated with silver powder, it forms:

A) Ethane B) Ethene C) Acetylene D) Methane

10. What is the reaction product of chloroform with conc. HNO3 in the presence of conc. H2SO4?

A) Picric acid B) Chloropicrin C) Nitrobenzene D) Benzene

11. Chloropicrin, formed from the reaction of chloroform with nitric acid, is used as a:

A) Anesthetic B) Fungicide and soil fumigant C) Solvent D) Refrigerant

12. The reaction of chloroform with a base like NaOH leads to the formation of:

A) Carbon monoxide B) Formate salt C) Carbon dioxide D) Methanol

13. Which of the following reagents can be used to detect the presence of chloroform?

A) Fehling's solution B) Tollens' reagent C) Silver nitrate solution (after hydrolysis) D) Potassium permanganate solution

14. Chloroform reacts with silver nitrate solution to give a precipitate of silver chloride. This reaction is indicative of:

A) Ionic chlorine B) Covalent chlorine C) Chlorine in the +1 oxidation state D) Free chlorine atoms

15. What happens when chloroform is exposed to air and sunlight for a long time?

A) It decomposes to form carbon tetrachloride B) It oxidizes to form phosgene (COCl2) C) It polymerizes to form a solid substance D) It reacts with air to form nitromethane

16. Phosgene (COCl2) is a highly toxic gas. Its formation from chloroform is a significant hazard. What is its common name?

A) Laughing gas B) Mustard gas C) Choking gas D) Tear gas

17. To prevent the oxidation of chloroform to phosgene, a small amount of which substance is usually added?

A) Ethanol B) Water C) Ammonia D) Sulphuric acid

18. What is the nature of the C-X bond in haloalkanes like chloroform?

A) Purely covalent B) Purely ionic C) Polar covalent D) Metallic

19. In the C-X bond of haloalkanes, the halogen atom is more electronegative than carbon. This leads to:

A) A partial positive charge on the halogen and a partial negative charge on carbon B) A partial negative charge on the halogen and a partial positive charge on carbon C) Equal sharing of electrons D) Complete transfer of electrons from carbon to halogen

20. The polarity of the C-X bond is responsible for:

A) The low boiling points of haloalkanes B) The reactivity of haloalkanes in nucleophilic substitution reactions C) The non-polar nature of haloalkanes D) The insolubility of haloalkanes in water

21. Which of the following is a mechanism for nucleophilic substitution reactions in haloalkanes?

A) Electrophilic addition B) Free radical substitution C) SN1 and SN2 mechanisms D) Elimination reactions

22. In the SN2 mechanism, the nucleophile attacks the carbon atom:

A) From the same side as the leaving group B) From the opposite side of the leaving group C) Simultaneously with the leaving group departure D) After the leaving group has completely departed

23. The SN2 reaction proceeds with:

A) Inversion of configuration B) Retention of configuration C) Racemization D) Epimerization

24. Which type of haloalkane is most reactive towards SN2 reactions?

A) Tertiary haloalkanes B) Secondary haloalkanes C) Primary haloalkanes D) Allylic and benzylic haloalkanes

25. In the SN1 mechanism, the rate-determining step is:

A) The attack of the nucleophile B) The departure of the leaving group to form a carbocation C) The combination of the nucleophile and carbocation D) The rearrangement of the carbocation

26. The SN1 reaction proceeds via:

A) A concerted, one-step process B) A two-step process involving a carbocation intermediate C) A multi-step radical chain mechanism D) An addition-elimination mechanism

27. Which type of haloalkane is most reactive towards SN1 reactions?

A) Primary haloalkanes B) Secondary haloalkanes C) Tertiary haloalkanes D) Methyl halides

28. What is the primary environmental concern associated with Freons (CFCs)?

A) Global warming B) Acid rain C) Ozone layer depletion D) Eutrophication

29. Freons are generally:

A) Highly reactive and flammable gases B) Inert, non-toxic, and non-flammable compounds C) Corrosive liquids D) Strong oxidizing agents

30. Which of the following is a common Freon used as a refrigerant?

A) DDT B) CCl4 C) Dichlorodifluoromethane (CCl2F2) D) CHCl3

31. How do Freons contribute to ozone layer depletion?

A) They react directly with ozone molecules B) They catalyze the decomposition of ozone in the stratosphere C) They form a protective layer that blocks UV radiation D) They increase the concentration of oxygen in the stratosphere

32. What is the role of chlorine radicals in ozone depletion caused by Freons?

A) They initiate the formation of ozone B) They break down ozone molecules (O3) into oxygen molecules (O2) C) They react with nitrogen oxides to form ozone D) They convert oxygen atoms into ozone

33. Which international agreement aims to phase out the production and consumption of ozone-depleting substances like Freons?

A) Kyoto Protocol B) Paris Agreement C) Montreal Protocol D) Basel Convention

34. DDT is a synthetic organochlorine compound. What does DDT stand for?

A) Dichlorodiphenyltrichloroethane B) Dichlorotriphenylmethane C) Diphenyltetrachloroethane D) Dichlorodiphenylethane

35. DDT was widely used as a:

A) Refrigerant B) Fungicide C) Insecticide D) Herbicide

36. Why was DDT banned in many countries?

A) It was ineffective against insects B) It caused rapid resistance in insects C) It is persistent in the environment and bioaccumulates D) It was too expensive to produce

37. The persistence of DDT in the environment means that it:

A) Breaks down quickly into harmless substances B) Remains in the soil and water for a very long time C) Is readily metabolized by most organisms D) Is easily washed away by rain

38. Bioaccumulation of DDT refers to its:

A) Rapid breakdown in organisms B) Excretion from the body C) Accumulation in the tissues of living organisms over time D) Conversion into other less harmful chemicals

39. Biomagnification of DDT refers to its:

A) Decrease in concentration at higher trophic levels B) Increase in concentration at higher trophic levels C) Uniform distribution throughout the food chain D) Complete absence in top predators

40. What is a significant ecological effect of DDT biomagnification?

A) Increased fertility in birds of prey B) Thinner eggshells in birds of prey, leading to reproductive failure C) Increased population of insects D) Improved water quality

41. Which of the following is a method for preparing carbon tetrachloride (CCl4) from chloroform?

A) Oxidation B) Reduction C) Heating with iron filings D) Heating with water

42. Carbon tetrachloride (CCl4) was formerly used as a:

A) Food preservative B) Refrigerant C) Dry cleaning solvent and fire extinguisher D) Fertilizer

43. What is a major health hazard associated with exposure to carbon tetrachloride?

A) Kidney damage B) Liver damage C) Lung irritation D) Skin rashes

44. The C-X bond strength in haloalkanes generally increases in the order:

A) C-I < C-Br < C-Cl < C-F B) C-F < C-Cl < C-Br < C-I C) C-Cl < C-Br < C-I < C-F D) C-I < C-F < C-Br < C-Cl

45. The dipole moment of haloalkanes decreases in the order:

A) CH3F > CH3Cl > CH3Br > CH3I B) CH3I > CH3Br > CH3Cl > CH3F C) CH3Cl > CH3Br > CH3F > CH3I D) CH3F > CH3Br > CH3Cl > CH3I

46. Which of the following is an example of a haloalkane that undergoes SN1 reactions readily due to carbocation stability?

A) Chloromethane B) 2-Chloropropane C) 2-Chloro-2-methylpropane (tert-butyl chloride) D) 1-Chloropropane

47. The reaction of chloroform with potassium hydroxide and ethanol is a method for the preparation of:

A) Carbon monoxide B) Formic acid C) Potassium formate D) Methanol

48. Which of the following is NOT a property of Freons?

A) Non-toxic B) Non-flammable C) Chemically reactive D) Low boiling points

49. The environmental effect of DDT is primarily related to its:

A) High solubility in water B) Rapid biodegradation C) Bioaccumulation and biomagnification D) Direct toxicity to plants

Preparation properties reactions nature of C-X bond mechanisms of substitution and environmental effects of chloroform freons and DDT - Online Test

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