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Free Chemistry of Hydrocarbons MCQs with Answers

1,091 Chemistry of Hydrocarbons MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Hydrocarbons are studied through the structures and reactions of alkanes, alkenes, alkynes and aromatic compounds. Coverage includes free radical substitution in alkanes, electrophilic addition to carbon-carbon multiple bonds, benzene substitution, aromatic stability and the difference between addition reactions of alkenes and substitution reactions of benzene.

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AlkanesFree Radical SubstitutionAlkenesAlkynesBenzene and Aromatic Compounds
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1,091 questions · page 39 of 55

761. A hydrocarbon, which is liquid at room temperature, decolourizes aqueous bromine. Which could be the molecular formula of the compound?

  • A. C2H2
  • B. C2H4
  • C. C7H16
  • D. C10H20

Explanation: Alkenes and Alkynes can decolorize bromine. so, the molecules must be either an alkyne or alkene.

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Correct answer: C10H20

762. ortho and para directing groups have all of the following properties EXCEPT:

  • A. They are not electron-donating groups
  • B. They increase reactivity of mono- substituted benzene ring
  • C. They facilitate the availabilty of electrons at ortho and para positions
  • D. Halogen-substituted benzene is more reactive than benzene

Explanation: Ortho para directing groups are electron donating and increase the reactivity of benzene ring hence, the statement given in option a:"They…

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Correct answer: They are not electron-donating groups

763. The termination step in chlorination of methane in presence of diffused sunlight is

  • A. CI2→ 2CI
  • B. CH4 +CI → CH3 +HCI
  • C. CI3CH+Cl → CCI4+HCl
  • D. H3C+CI2 → H3CCI+Cl

Explanation: Termination step in free radical substitution mechanism involvesi) Attack of free radical on other free radicalii) Bond formationiii)…

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Correct answer: CI3CH+Cl → CCI4+HCl

764. Among the following the compound that can be most readily nitrated is:

  • A. Benzoic acid
  • B. Benzene
  • C. Phenol
  • D. Chlorobenzene

Explanation: In Phenol, an OH group is attached to Benzene.OH group is an electron donating group and increases the reactivity of benzene ring due to…

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Correct answer: Phenol

765. How carboxylic acid group attached to benzene ring affects its reactivity?

  • A. Make it reactive
  • B. Makes ortho position of benzene more reactive than others
  • C. Makes meta position of benzene more reactive than others
  • D. Makes para position of benzene more reactive than others

Explanation: Option C is correct. The carboxylic acid group is an electron-withdrawing group due to the electronegativity of the oxygen atom.

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Correct answer: Makes meta position of benzene more reactive than others

766. Ten moles of hydrogen are allowed to react with 6 moles of oxygen. How much water will be obtained from the reaction on complete consumption of one gas?

  • A. 10 moles
  • B. 8 moles
  • C. 5 moles
  • D. 4 moles

Explanation: The reaction to form water is 2H2 + O2=2H2O.In this reaction we can see that the amount of moles of hydrogen decides the number of moles…

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Correct answer: 10 moles

767. Skeletal formula of an organic compound iv given below:It is a hydrocarbonIUPAC name of the compound is:

  • A. 3, 3-Dimethyl-3-hexene
  • B. 3, 4-Dimethyl-3-hexene
  • C. 3-Hexene
  • D. 2,3-Dimethyl-1-hexene

Explanation: Option B is correct as all positions of the functional group i.e the double bond and the methyl branches are represented…

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Correct answer: 3, 4-Dimethyl-3-hexene

768. Which one of the following is a powerful electrophile used to attack the electrons of the benzene ring?

  • A. FeCl2
  • B. FeCl4-
  • C. Cl+
  • D. Cl2

Explanation: Cl+ is a powerful electrophile and is capable of attacking the electrons of the benzene ring in electrophilic aromatic substitution…

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Correct answer: Cl+

769. Find the error of Article.It is hoped to have everything in order for first performance at the end of November.

  • A. To have
  • B. In
  • C. First
  • D. At

Explanation: The phrase "first performance" is missing an article. It should be "the first performance." The sentence should read: "It is hoped to have…

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Correct answer: First

770. A large amount of money----- stolen in last nights bank robbery.

  • A. is
  • B. are
  • C. was
  • D. were

Explanation: The correct answer is 'was', which is the singular past tense form of the verb 'be' and properly agrees with the singular subject, 'a…

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Correct answer: was

771. Each sentence below has a blank indicating that something has been omitted. Choose the word that best fits in with the meaning of the sentence as a whole.The _ climate of the island made life uncomfortable for the locals; one minute it is raining, the next minute it would be sweltering.

  • A. Congruous
  • B. Frigid
  • C. Immaculate
  • D. Capricious

Explanation: After the semicolon, it is revealed that the climate is raining one minute, and very hot ("sweltering") the next minute.

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Correct answer: Capricious

772. Directions: Read the following information and give answer.There is a family of six persons E, I, R. K, T, and Y. I and R are sisters. T is mother of R and E is son-in-law of K. K is father of T and I is mother of YHow is R is related to Y?

  • A. Aunt
  • B. Niece
  • C. Sister
  • D. Mother

Explanation: To determine R's relationship to Y, start by mapping out the family relationships:1.

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Correct answer: Aunt

773. In this question, a statement is given followed by two courses of action numbered I and II. It is required to grasp the statement, analyze the problem or policy it mentions and then decide which of the courses of action logically follow / most appropriate.Statement:The Kharif crops have been affected by the insects for consecutive three years in the district and the farmers harvested less than fifty percent of produce during these years.Courses of action:I) The farmers should seek measures to control the attack of insects to protect their crops next year.II) The Government should increase the support price of Khalif crops considerably to protect the economic interests of farmers.

  • A. If only I follows
  • B. If only II follows
  • C. If either I or II follows
  • D. If neither I nor II follows
  • E. If both I and II follow

Explanation: The correct answer is E: Both I and II follow. The first course of action, I), focuses on long-term agricultural health by suggesting that…

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Correct answer: If both I and II follow

774. In this section of logical deduction, the question consists of a brief passage (usually a report containing certain data regarding some social or economic problem), followed by certain inferences based on it. The student is required to analyze the contents (or data) of the passage and grasp the desirable facts from it. Then, student has to consider each of the given inferences in the context of the given passage. decide upon its degree of truth or falsity and then choose the hest alternative provided accordingly.A radical new surgery procedure, laughed at not long ago, is holding out fresh hope for patients of cardiac myopathy, or enlargement of the heart. The technique, now in Pakistan, allows patients to go home two weeks after the Operation, to lead a near-normal sedentary life. Cardiac myopathy is a condition that has a variety of causative factors. An attack from one of the 20 identified viruses, parasite infection, long-term alcohol abuse and blood pressure could bring it on, and in rare cases, it could follow child birth and is even known to run in families. The condition is marked by an increase in the size of the heart's chambers and a decrease in the efficiency of pumping.Earlier the patients suffering from cardiac myopathy were required to travel abroad for such operation.

  • A. Definitely true
  • B. Probably true
  • C. Data inadequate
  • D. Probably false
  • E. Definitely false

Explanation: The correct answer is Data inadequate because while the passage gives an optimistic view of the new surgical procedure in Pakistan, it…

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Correct answer: Data inadequate

775. In the following question, two statements numbered I and II are given. There may be cause and effect relationship between the two statements. These two statements may be the effect of the same cause or independent causes. These statements may be independent causes without saving any relationship. Read both the statements in question and mark your answer as:A. If statement I is the cause and statement II is its effect;B. If statement II is the cause and statement, I is its effect;C. If both the statements I and II are independent causes;D. If both the statements I and II are effects of independent causes;E. If both the statements I and II are effects of some common causes;I. Majority of the students in the college expressed their Opinion against the college authority's decision to break away from the university and become autonomous.II. The university authorities have expressed their inability to provide grants to its constituent colleges.

  • A. If statement I is the cause and statemerit ats effect;
  • B. If statement II is the cause and statement, I is its effect:
  • C. If both the statements I and II are independent causes;
  • D. If both the statements I and II are effects of independent causes;
  • E. If both the statements I and II are effects of some common cause;

Explanation: The correct answer is Option B. The university's inability to provide grants (Statement II) is likely a reason for the college's decision…

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Correct answer: If statement II is the cause and statement, I is its effect:

776. Find the missing term in the sequence: 0, 7, 15, 24, 34, ?

  • A. 55
  • B. 45
  • C. 46
  • D. 50

Explanation: The pattern is n² - 1, starting with n=1. 1²-1=0, 3²-2=7, 4²-1=15, 5²-1=24, 6²-2=34. Correction: The pattern seems inconsistent.

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Correct answer: 45

777. Which one of the following free radical is most stable:

  • A. CH3*
  • B. (CH3)2CH*
  • C. (CH3)3C*
  • D. C2HS*

Explanation: Attachment of the alkyl group increases the stability of free radicals as alkyl groups are electron donating through the hyperconjugation…

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Correct answer: (CH3)3C*

778. Consider reversibility in free radical substitution reaction of alkane then Kc value is smallest for:

  • A. Initiation step
  • B. Propagation step
  • C. Termination step
  • D. All same

Explanation: In a free radical substitution reaction of an alkane, the reaction can proceed through several steps involving free radicals (species with…

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Correct answer: Termination step

779. In the presence of hot alkaline potassium permanganate solution 2-butene will give

  • A. Formic acid + acetic acid
  • B. Two moles of methanoic acid
  • C. Two moles of ethanoic acid
  • D. Ethylene glycol

Explanation: 2-butene is a symmetrical alkene, and when it undergoes oxidative cleavage with hot alkaline KMnO4, each carbon-carbon double bond is…

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Correct answer: Two moles of ethanoic acid

780. Benzene does not undergo:

  • A. Addition
  • B. Substitution
  • C. Polymerization
  • D. Aromatization

Explanation: Benzene does not undergo polymerisation reaction due to the aromaticity of the ring.

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Correct answer: Polymerization
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