CBSE Class-12 Exam 2020 : Question Paper (Chemistry)
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Class-12 Exam 2020 : Question Paper (Chemistry)
- Subject :- Chemistry
- Class : XII
- Year : 2020
SECTION A
Read the given passage and answer the questions number 1 to 5 that follow : 1x5=5
The substitution reaction of alkyl halide mainly occurs by SN1 or SN2 mechanism. Whatever mechanism alkyl halides follow for the substitution reaction to occur, the polarity of the carbon halogen bond is responsible for these substitution reactions. The rate of SN1 reactions are governed by the stability of carbocation whereas for SN2 reactions steric factor is the deciding factor. If the starting material is a chiral compound, we may end up with an inverted product or racemic mixture depending upon the type of mechanism followed by alkyl halide. Cleavage of ethers with HI is also governed by steric factor and stability of carbocation, which indicates that in organic chemistry, these two major factors help us in deciding the kind of product formed.
1. Predict the stereochemistry of the product formed if an optically active alkyl halide undergoes substitution reaction by SN1 mechanism.
2. Name the instrument used for measuring the angle by which the plane polarised light is rotated.
3. Predict the major product formed when 2-Bromopentane reacts with alcoholic KOH.
4. Give one use of CHI3
5. Write the structures of the products formed when anisole is treated with HI.
Questions number 6 to 10 are one word answers : 1x5=5
6. Identify which liquid will have a higher vapour pressure at 900C if the boiling points of two liquids A and B are 1400C and 1800C, respectively.
7. Out of zinc and tin, whose coating is better to protect iron objects ?
8. Will the rate constant of the reaction depend upon T if the Eact (activation energy) of the reaction is zero ?
9. Give the structure of the monomer of PVC.
10. Which structural unit present in a detergent makes it non-biodegradable ?
Questions number 11 to 15 are multiple choice questions : 1x5=5
11. Out of the following, the strongest base in aqueous solution is
(A) Methylamine
(B) Dimethylamine
(C) Trimethylamine
(D) Aniline
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