Hydrocarbons

Class 11th Chemistry – 13 Hydrocarbons MCQs

The impurities found in the preparation of acetylene are ____.

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The impurities found in the preparation of acetylene are phosphine and carbon monoxide. Acetylene contains the impurities of hydrogen sulphide and phosphine due to the presence of calcium sulphide and calcium phosphide in calcium carbide, as impurities.

With ____, the reaction of alkene is explosive.

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With fluorine, the reaction of alkene is explosive. All alkenes react vigorously with fluorine. The vigour of the reactions with the halogens decreases down the group, and reactions with iodine are relatively slow.

Gasoline, kerosene and diesel are obtained by destructive distillation of ____.

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Gasoline, kerosene and diesel are obtained by destructive distillation of petroleum. Petroleum deposits are usually covered with a gaseous mixture called natural gas. Thus, gasoline, kerosene and diesel are obtained by destructive distillation of petroleum found under the earth's crust.

Which one of the following cannot be prepared by Wurtz reaction?

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CH4 has only one carbon atom, hence it can’ be prepared by Wurtz reaction, which involves two molecules of alkyl halide.

The IUPAC name of the compound CH3CH = CH2=CH is Pent-l-yn-3-ene

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When both double and triple bonds are present, then triple bond is considered as the principal group.

The electron dot representation of covalent molecules is also called ____.

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Electron representation of the covalent molecule is called as Lewis structure. Lewis was the first person to explain the covalent structure with the dots representing the valence electrons of the atom, combining with the other atoms.

Tollens reagent is ____.

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Tollens' reagent is ammonical silver nitrate solution. The formula of Tollens' reagent is [Ag(NH3)2]+ OH-.

Propyne and propene can be distinguished by

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Ammonical silver nitrate and ammonical cuprous chloride give precipitate only with terminal alkynes (propyne, CH3 =CH)

Replacement of hydrogen from first carbon atom of n-propane by CH3 gives ____.

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Replacement of hydrogen from first carbon atom of propane by CH3 gives n-butane. n-propane - CH3 - CH2 - CH3 Replacing hydrogen atom of first carbon atom - CH3 - CH2 - CH2 - CH3 n-butane - CH3 - CH2 - CH2 - CH3.

Benzene present in ____is obtained by fractional distillation of coal tar.

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Benzene present in light oil is obtained by fractional distillation of coal tar. Benzene is mainly present in the light oil fraction of coal tar distillation, from where it is isolated by suitable methods.

The general formula for cycloalkanes is ____.

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The general formula for cycloalkanes is CnH2n. It is also called monocyclic due to the presence of single ring structure. The general formula of alkenes is also CnH2n.

Huckel’s rule states that a monocyclic conjugated compound will be aromatic if it contains

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Huckel’s rule states that for aromaticity there must be (4n + 2) π electrons present in compound where n is an integer.

The ratio of number of σ bonds to π bonds in napthalene is ____.

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The number of σ bonds and π bonds in napthalene are 19 and 5 respectively

The term carcinogenic means ____.

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The term carcinogenic means producing cancer. Some chemicals have the property of producing cancer, when people are exposed to it continuously. Such chemicals are called as carcinogenic agents or cancer producing agents.

When tetrabromoethane is heated with zinc, it gives _____ .

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When tetrabromoethane is heated with zinc, it gives ethyne. The reaction is as follows: When tetrabromoethane is heated with zinc, it gives ethyne and zinc bromide. Br2CH - CHBr2 + 2 Zn ----------CH ≡ CH + 2 ZnBr2.

3- Hexyne reacts with Na/liq.NH3 to produce

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Reduction of alkynes with Na/liq. NH3 gives trans-alkenes.

But-1-ene and 2-methylpropene exhibit ____.

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But-1-ene and 2-methylpropene exhibit chain isomerism. The structure of But-1-ene is CH3 -CH2 - CH = CH2 The structure of 2-methylpropene is CH2 = C(CH3) - CH3 Both structures have the same molecular formula C4H8. The difference in the structure is due to the difference in the structure of the carbon chain.

Which one of the following has highest boiling point?

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n-Octane has highest boiling point due to unbranched chain and maximum carbon atoms. It has max. Van der Waal’s forces.

The resonance energy of benzene is ____.

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The resonance energy of benzene is 150 kJ mol-1.The difference between the energy of the most stable contributing structure and the energy of the resonance hybrid is known as resonance energy.

The possible combinations of disubstituted products of benzene are ____.

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The possible combinations of disubstituted products of benzene are ortho and para. The already existing functional group will direct the incoming group to either ortho and para positions simultaneously or to meta position. Except these, no other combination is possible.

The primary target for carcinogenic hydrocarbons in the human body is ____.

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The primary target for carcinogenic hydrocarbons in the human body is deoxyribonucleic acid. This is also known as DNA. Other parts that will be affected by carcinogens is the RNA (ribonucleic acid) in the living organisms.

____ has garlic smell.

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Ethyne has garlic smell. All the alkynes are odourless. However, acetylene (ethyne) has garlic smell due to the presence of phosphine as impurity.

Arrange the following hydrogen halides in order of their decreasing reactivity with propane.

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Without hint.

In ____, the bonds are non-directional.

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In RbCl, the bonds are non-directional. The first three options are covalent compounds which are directional. The dipole moment may be zero or greater than one. In RbCl, it is purely ionic, as Rhubidium is an alkali metal.

What are aromatic hydrocarbons commonly known as?

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Aromatic hydrocarbons are commonly known as arenes (aromatic alkenes)

The total number of conformations of ethane are____.

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The total number of conformations of ethane are infinite. Since rotation around C - C bond of ethane is continuous, there are infinite number of conformations. However, only two are major. These are the lowest energy structure called staggered conformation and the highest energy structure called eclipsed conformation.

The reaction which does not give an alkane is ____.

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The reaction which does not give an alkane is dehydrohalogenation of an alkyl halide. All other methods give alkane, whereas dehydrohalogenation of an alkyl halide gives an alkene.

The function of anhydrous AlCl3 in Friedel Craft's reaction is to ____.

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In electrophilic substitution reactions of benzene, generation of an electrophile is the major step. Anhy AlCl3 is a Lewis acid reacts with the reagents to generate an electrophile. For eg in FC alkylation AlCl3 + RCl → AlCl4- + R+ (Electrophile).

Arrange the halogens F2, Cl2, Br2, I2,in order of their increasing reactivity with alkanes.

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Without hint.

With respect to the conformations of a hydrocarbons, ____change/s.

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With respect to the conformations of a hydrocarbons, distance between non-bonded H-atoms changes. In conformations of hydrocarbons, only the distance between the non-bonded hydrogen atoms changes, while all bond distances and bond angles remain to be the same.

Class 11th Chemistry - 13 Hydrocarbons MCQs
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Class 11th Chemistry - 13 Hydrocarbons MCQs