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Assertion and Reason Questions on Class 12 Chemistry Chapter 10 HALOALKANES AND HALOARENES

Directions: These questions consist of two statements, each printed as Assertion and Reason. While answering these questions, you are required to choose any one of the following four responses.
(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
(c) If the Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.

Q.1. Assertion : SN2 reaction of an optically active aryl halide with an aqueous solution of KOH always gives an alcohol with opposite sign of rotation.
Reason : SN2 reactions always proceed with inversion of configuration.

Answer (d) Assertion is false, because aryl halides do not undergo nucleophilic substitution under ordinary conditions. This is due to resonance, because of which the carbon– chlorine bond acquires partial double bond character, hence it becomes shorter and stronger and thus cannot be replaced by nucleophiles. However Reason is true.

Q.2. Assertion : Alkylbenzene is not prepared by Friedel-Crafts alkylation of benzene.
Reason : Alkyl halides are less reactive than acyl halides.

Answer (c) Alkyl halides give polyalkylation products.

Q.3. Assertion : Exposure of ultraviolet rays to human causes the skin cancer, disorder and disrupt the immune system.
Reason : Carbon tetrachloride is released into air it rises to atmosphere and deplets the ozone layer.

Answer (b) Carbon tetrachloride rises to atmosphere and deplete the ozone layer. This depletion of ozone layer increases exposure of UV rays to human being which lead to increase of skin cancer, eye diseases and disorder with disruption of the immune system.

Q.4. Assertion : CHCl3 is stored in dark bottles.
Reason : CHCl3 is oxidised in dark.

Answer (c) CHCl3 is stored in dark bottles to prevent oxidation of CHCl3 in presence of sunlight.

Q.5. Assertion : CCl4 is not a fire extinguisher.
Reason : CCl4 is insoluble in water.

Answer (d) CCl4 is used as a fire extinguisher. The dense, non combustible vapours cover the burning substance and prevents the availability of oxygen around burning material.


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