Chemistry MCQs Set 3 Frequently Asked Questions in Exams

This section contains chemistry MCQs designed to test your chemistry knowledge and aid in your preparation for competitive exams. Practicing these questions enhances comprehension of fundamental chemistry principles and boosts exam performance. It’s worth noting that these questions are frequently asked in various exams, making them an excellent resource for exam preparation.

1. What is the hybridization of the carbon atom in the carbonyl group?
a. sp hybrid
b. sp2 hybrid
c. sp3 hybrid
d. sp4 hybrid
Answer: b. sp2 hybrid

2. Which of the following compounds does not undergo Cannizzaro’s reaction?
b. C6H5CHO
c. (CH3)3CCl
Answer: a. CH3CHO

3. Which reaction involves the treatment of an aromatic aldehyde with an acid anhydride in the presence of the corresponding salt of the acid to produce an unsaturated aromatic acid?
a. Perkin reaction
b. Cannizzaro reaction
c. Friedel-Crafts acylation
d. Claisen condensation
Answer: a. Perkin reaction

4. What is the product of the aldol reaction upon heating?
a. Acetaldehyde
b. Crotonaldehyde
c. Phoron
d. Acetophenone
Answer: b. Crotonaldehyde

5. What is the typical source for the synthesis of ketones through oxidation?
a. Primary alcohol
b. Secondary alcohol
c. Tertiary alcohol
d. All of these
Answer: b. Secondary alcohol

6. When alcohol is added to carbonyl compounds to form an acetal, the geometry of the acetal is:
a. Linear
b. Trigonal
c. Tetrahedral
d. Planar
Answer: c. Tetrahedral

7. When HCN is added to carbonyl compounds, the reaction is categorized as:
a. Electrophilic addition
b. Radical polymerization
c. Electrophilic substitution
d. Nucleophilic addition
Answer: d. Nucleophilic addition

8. Which reagent will give similar results for both butanal and butanone?
a. Tollen’s reagent
b. I2 + aq. NaOH
c. Fehling’s solution
d. 2,4-Dinitrophenylhydrazine reagent
Answer: d. 2,4-Dinitrophenylhydrazine reagent

9. Among the following methods, which one does not yield aldehydes?
a. Hydration of alkynes
b. Oxidation of primary alcohol
c. Oxidation of secondary alcohol
d. Gatterman reaction
Answer: c. Oxidation of secondary alcohol

10. Which class of compounds is frequently used for artificial flavoring in jams and similar products?
a. Alcohols
b. Carboxylic acid
c. Esters
d. Ketones
Answer: c. Esters

11. Acetic acid is typically produced through the fermentation of:
a. Methanol
b. Ethanol
c. Propanol
d. Butanol
Answer: b. Ethanol

12. Acetamide is subjected to different reagents individually. Which of the following reagents will result in the formation of methylamine?
a. Soda lime
b. PCl5
c. NaBH4
d. NaOH – Br2
Answer: d. NaOH – Br2

13. Statement 1: Carboxylic acids often form dimers in the vapor phase or in aprotic solvents.
Statement 2: Higher carboxylic acids tend to have limited solubility in water.
a. Both statements are true, and Statement 2 is the reason for Statement 1
b. Both statements are true, but Statement 2 is not the reason for Statement 1
c. Statement 1 is true, but Statement 2 is false
d. Statement 1 is false, but Statement 2 is true
Answer: b. Both statements are true, but Statement 2 is not the reason for Statement 1

14. What are the products formed when benzaldehyde and formaldehyde are heated with aqueous NaOH solution?
a. Benzyl alcohol + methanol
b. Sodium benzoate + sodium formate
c. Benzyl alcohol + sodium formate
d. Sodium benzoate + methanol
Answer: c. Benzyl alcohol + sodium formate

15. Which of the following compounds undergoes tautomerism?
a. Acetaldehyde
b. Acetophenone
c. Benzoic acid
d. Acetone
Answer: a. Acetaldehyde

16. Among the following compounds, which one possesses the most acidic hydrogen?
a. Hexane-2,3-dione
b. Hexane-2,5-dione
c. Hexane-3-one
d. Hexane-2,4-dione
Answer: d. Hexane-2,4-dione

17. In a Wolff-Kishner reduction, which conversion is achieved?
a. Acetone into isopropanol
b. Acetaldehyde into ethanol
c. Acetophenone into diphenylmethane
d. Acrolein into allyl alcohol
Answer: c. Acetophenone into diphenylmethane

18. What type of reaction occurs when a ketone forms a cyanohydrin?
a. Electrophilic addition
b. Nucleophilic substitution
c. Nucleophilic addition
d. Electrophilic substitution
Answer: c. Nucleophilic addition

19. Which compound is produced when ethyl formate reacts with excess CH3MgI, followed by hydrolysis?
a. Isopropyl alcohol
b. Ethanol
c. n-Propyl alcohol
d. Propanal
Answer: a. Isopropyl alcohol

20. Formic acid and acetic acid can be differentiated by their reactivity with which reagent?
a. Sodium ethoxide
b. Sodium
c. 2,4-dinitrophenylhydrazine
d. HgCl2
Answer: d. HgCl2

21. In the presence of excess chlorine and diffused sunlight, the final product of the reaction between methane and chlorine is:
a. Chloroform
b. Carbon tetrachloride
c. Dichloromethane
d. Methyl chloride
Answer: b. Carbon tetrachloride

22. What gas is commonly used for the artificial ripening of fruits?
a. Ethylene gas
b. Methane gas
c. Propane
d. Carbon dioxide
Answer: a. Ethylene gas

23. What type of isomerism is exhibited by alkanes?
a. Skeletal
b. Position
c. Geometric
d. Metamerism
Answer: a. Skeletal

24. Which of the following alkanes contains only primary hydrogen atoms?
a. Pentane
b. Neopentane
c. Isopentane
d. 2,2-dimethylbutane
Answer: b. Neopentane

25. What type of reaction is the halogenation of alkanes?
a. Electrophilic substitution
b. Free radical substitution
c. Nucleophilic substitution
d. Oxidation
Answer: b. Free radical substitution

26. In the Wolf-Kishner reduction, aldehydes are converted into:
a. Alkynes
b. Alkenes
c. Alkanes
d. Alcohol
Answer: c. Alkanes

27. Alkanes are non-polar molecules and are soluble in:
a. Diethyl ether
b. Benzene
c. Toluene
d. All of these
Answer: d. All of these

28. Which type of reactions do alkanes undergo?
a. Addition
b. Substitution
c. Elimination
d. Polymerization
Answer: b. Substitution

29. Among the following conformations of n-butane, which is the most stable?
a. Eclipsed
b. Skew Boat
c. Gauche
d. Staggered
Answer: d. Staggered

30. What is the bond angle between H-C-C bonds in ethane?
a. 120°
b. 180°
c. 109°
d. 109.5°
Answer: d. 109.5°

31. Choose the correct order for the ease of formation of free radicals:
a. 1°>2°>3°
b. 3°>2°>1°
c. 2°>1°>3°
d. 2°>3°>1°
Answer: b. 3°>2°>1°

32. Formation of an alkane from the reduction of an alkyl halide with Zn is known as…?
a. Cannizaro’s reaction
b. Frankland reaction
c. Kolbe’s reaction
d. Wurtz reaction
Answer: b. Frankland reaction

33. How many hydrogen atoms does a 7-carbon alkane have?
a. 20
b. 16
c. 14
d. 12
Answer: b. 16
Explanation: For an alkane, the general formula is CnH2n+2, where “n” represents the number of carbon atoms. So, for a 7-carbon alkane:
C7H2(7) + 2 = C7H16
Therefore, a 7-carbon alkane will have 16 hydrogen atoms.

34. Select the correct range of carbon atoms required for a molecule to be classified as a higher alkane.
a. 17-40 carbon atoms
b. 1-4 carbon atoms
c. 5-16 carbon atoms
d. 41 or above
Answer: a. 17-40 carbon atoms

35. The compound with the highest boiling point among the following is:
a. n-Butane
b. n-Octane
c. 2,2,3,3-Tetramethylbutane
d. Iso-octane
Answer: c. 2,2,3,3-Tetramethylbutane

36. The correct order for relative energies of the ethane conformations is:
a. skewed < staggered < eclipsed
b. skewed < eclipsed < staggered
c. staggered < eclipsed < skewed
d. staggered < skewed < eclipsed
Answer: d. staggered < skewed < eclipsed

37. Find the alkane (C5H12) that will yield only one type of monohalogenated compound.
a. 2-methylbutane
b. cyclopentane
c. n-pentane
d. 2,2-dimethylpropane
Answer: d. 2,2-dimethylpropane

38. Which of the following alkanes is the most volatile?
a. 2,2-dimethylpropane
b. isobutane
c. 2-methylbutane
d. n-pentane
Answer: a. 2,2-dimethylpropane

39. What is another name for branched-chain alkanes?
a. Paraffins
b. Neoparaffins
c. Isoparaffins
d. Naphthenes
Answer: c. Isoparaffins

40. Which of the following statements is not true about alkanes?
a. Alkanes are saturated hydrocarbons
b. Alkanes have a general formula of CnH2n+2
c. Alkanes are the simplest hydrocarbons
d. Alkanes are all solids at room temperature
Answer: d. Alkanes are all solids at room temperature

41. In ethene, each hydrogen atom has one unpaired electron, and each carbon is:
a. sp³ hybridized
b. sp² hybridized
c. sp hybridized
d. Not hybridized
Answer: b. sp² hybridized

42. Alkenes typically undergo which type of reaction?
a. Substitution reaction
b. Elimination reaction
c. Addition reaction
d. Rearrangement reaction
Answer: c. Addition reaction

43. What is the product obtained when 1-chlorobutane reacts with alcoholic potash?
a. 1-Butene
b. 2-Butene
c. 1-Butanol
d. 2-Butanol
Answer: a. 1-Butene

44. The position of a double bond in alkenes can be determined using:
a. Bromine water
b. Ozonolysis
c. Ammonical silver nitrate solution
d. Baeyer’s reagent
Answer: b. Ozonolysis

Recommended: Alkenes Practice Test

45. What is the name of the polymer formed from ethene?
a. Polypropylene
b. Polyethylene
c. Polystyrene
d. Polyvinyl chloride
Answer: b. Polyethylene

46. What is the most commonly used catalyst in the polymerization of ethene?
a. Ziegler-Natta catalysts
b. Aluminium triethyl
c. Metallocene catalysts
d. Free radical initiators
Answer: a. Ziegler-Natta catalysts

47. Which is the first member of the alkene family?
a. Pentene
b. Methane
c. Ethylene
d. Acetylene
Answer: c. Ethylene

48. When propene reacts with HBr in the presence of peroxide, what product is formed?
a. Allyl bromide
b. Isopropyl bromide
c. 3-bromopropane
d. n-propyl bromide
Answer: d. n-propyl bromide

49. Which of the following alkenes exhibits the maximum stability?
a. Cis-2-butene
b. 1-Butene
c. Trans-2-butene
d. 2-Methylpropene
Answer: c. Trans-2-butene

50. What is the product obtained when ethylene bromide is treated with Zn?
a. Alkyne
b. Alkane
c. Ethane
d. Alkene
Answer: d. Alkene

51. What causes cis-trans isomerism in alkenes?
a. Restricted rotation about the double bond
b. Different numbers of carbon atoms
c. Free rotation about double bond
d. Free rotation about single bond
Answer: a. Restricted rotation about the double bond

52. Which of the following will yield 2 acetaldehyde molecules upon ozonolysis?
a. 1-pentene
b. 2-butene
c. 2-pentene
d. 1-butene
Answer: b. 2-butene

53. Which of the following compounds exhibits geometrical (cis-trans) isomerism?
a. 2-Butene
b. 2-Butyne
c. 2-Butenol
d. Butanol
Answer: a. 2-Butene

54. Among the following, which compound is the most reactive?
a. Ethane
b. Ethene
c. Ethyne
d. Benzene
Answer: c. Ethyne

55. In alkenes, the carbon atoms are connected to each other by a:
a. Single bond
b. Triple bond
c. Covalent bond
d. Double bond
Answer: d. Double bond

56. When an alkene undergoes hydroboration-oxidation, what is the stereochemistry of the resulting alcohol?
a. Racemic mixture
b. Retention of configuration
c. Inversion of configuration
d. Mixture of retention and inversion
Answer: b. Retention of configuration

57. You are conducting an experiment to identify an unknown alkene. You add bromine water to an unknown alkene, and the reddish-brown color disappears. What can you conclude?
a. An unsymmetrical alkene
b. A symmetrical alkene
c. A trans-alkene
d. A cis-alkene
Answer: a. An unsymmetrical alkene

58. Which of the following compound exhibits the E-Z isomerism in its structure?
a. 2-methylpent-2-ene
b. 2,3-methylpentene
c. 3-methylpent-2-ene
d. 2,3-dimethylpent-2-ene
Answer: c. 3-methylpent-2-ene

59. Which of the following alkenes is represented by the name “4-chlorobut-1-ene”?
a. 1-Chloro-2-butene
b. 2-Chloro-1-butene
c. 2-Chloro-2-butene
d. 3-Chloro-1-butene
Answer: d. 3-Chloro-1-butene

60. You are tasked with distinguishing between two unknown alkenes, A and B. Alkene A is treated with a cold, dilute potassium permanganate (KMnO4) solution, and there is no color change. Alkene B, when treated with the same reagent, decolorizes the solution. Which of the following statements is true?
a. Alkene A is more substituted than alkene B
b. Alkene A is less substituted than alkene B
c. Alkene A is cis, and alkene B is trans
d. Alkene A is trans, and alkene B is cis
Answer: b. Alkene A is less substituted than alkene B
Explanation: Alkenes with more substitution (more alkyl groups attached to the double bond) are more stable and do not readily react with cold, dilute KMnO4, whereas less substituted alkenes can be oxidized by KMnO4.