Assertion Reason Chemistry Chapter 6 Haloalkanes and Haloarenes
Questions of Assertion Reason of Chemistry Chapter 6 Haloalkanes and Haloarenes CBSE Class 12 are very simple to understand as this chapter deals with Haloalkanes and Haloarenes. To solve assertion reason type questions of Chemistry, a deeper understanding of concept about Classification, Nomenclature, Nature of C–X Bond, Methods of Preparation of Haloalkanes, Preparation of Haloarenes, Physical Properties, Chemical Reactions and Polyhalogen Compounds is required. In order to help the student in solving Assertion Reason type of questions, detailed process is explained.
How to solve Assertion Reason Type Questions?
In Assertion-Reason type of question, two statements are given, first is Assertion and second is called Reason. Student must have to think critically about both the statements in Assertion Reason Questions, since it combines multiple choice questions and true/false type of questions which requires a higher level of understanding.
How many types are there of Assertion Reason Type Questions?
Assertion-Reason type of questions can be asked either with four MCQ options or with five MCQ options. First four options are same in both the cases only one more options is being provided i.e. last one. One extra option increases the difficulty level of the questions.
In assertion reason type of questions, all 4 or 5 options are same for each question, which are as:
(a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
(b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
(c) Assertion (A) is true but reason (R) is false.
(d) Assertion (A) is false but reason (R) is true.
(e) Both Assertion and Reason are false.
Then a question haunts in every student’s mind, which option is correct and when?
This can be understood clearly with the following table:
| Assertion (A) | Reason (R) | MCQ Options (Fixed for all questions) |
|---|---|---|
| If True | True | (a) Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A). |
| If True | True | (b) Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A). |
| If True | False | (c) Assertion (A) is true but reason (R) is false. |
| If False | True | (d) Assertion (A) is false but reason (R) is true. |
| If False | False | (e) Both Assertion and Reason are false. |
Now, lets practice some Assertion Reason Questions of Chemistry: Chapter 6 Haloalkanes and Haloarenes
Read instructions carefully before answering the questions.
For question given below, two statements are given- one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:
(a) Both A and R are true and R is correct explanation of the assertion.
(b) Both A and R are true but R is not the correct explanation of the assertion.
(c) A is true but R is false.
(d) A is false but R is true.
Question.1.
Assertion : SN^{2} reaction of an optically active aryl halide with an aqueous solution of KOH always gives an alcohol with opposite sign of rotation.
Reason : SN^{2} reactions always proceed with inversion of configuration.
Ans.1. (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.
Question.2.
Assertion : Alkylbenzene is not prepared by Friedel-Crafts alkylation of benzene.
Reason : Alkyl halides are less reactive than acyl halides.
Ans.2. (c)
Alkyl halides give polyalkylation products.
Question.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.
Ans.3. (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.
Question.4.
Assertion : CHCl_{3} is stored in dark bottles.
Reason : CHCl_{3} is oxidised in dark.
Ans.4. (c)
CHCl_{3} is stored in dark bottles to prevent oxidation of CHCl_{3} in presence of sunlight.
Question.5.
Assertion : CCl_{4} is not a fire extinguisher.
Reason : CCl_{4} is insoluble in water.
Ans.4. (d)
CCl_{4} is used as a fire extinguisher. The dense, non combustible vapours cover the burning substance and prevents the availability of oxygen around burning material.
