Subject

Chemistry

Class

CBSE Class 12

Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

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 Multiple Choice QuestionsShort Answer Type

21.

What is the cause of a feeling of depression in human beings? Name a drug which can be useful in treating this depression.

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22.

Explain the following behaviours:

(i) Alcohols are more soluble in water than the hydrocarbons of comparable molecular masses.

(ii) Ortho-nitro phenol is more acidic than ortho-methoxyphenol.

653 Views

23.

Explain the mechanism of acid catalysed hydration of an alkene to form corresponding alcohol.

2416 Views

24.

Complete the following chemical reaction equations:

(i) C6H5N2Cl + H3PO2+ H2O --->

(ii) C6H5NH2+ Br2(aq.)--->

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25.

Describe the following giving the relevant chemical equation in each case:

(i) Carbylamines reaction

(ii) Hofmann’s bromamide reaction.


(i) Carbylamines reaction

Carbylamines reaction is used as a test for the identification of primary amines. When aliphatic and aromatic primary amines are heated with chloroform and ethanolic potassium hydroxide, carbylamines (or isocyanides) are formed. These carbylamines have very unpleasant odours.

Secondary and tertiary amines do not respond to this test.

 

For example, 

 

(b) Hoffmann bromamide reaction

When an amide is treated with bromine in an aqueous or ethanolic solution of sodium hydroxide, a primary amine with one carbon atom less than the original amide is produced. This degradation reaction is known as Hoffmann bromamide reaction. This reaction involves the migration of an alkyl or aryl group from the carbonyl carbon atom of the amide to the nitrogen atom.

 

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26.

Differentiate between disinfectants and antiseptics. Give one example of each group.

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27.

Answer the following question:

(i) What is meant by the chirality of a compound? Give an example.

(ii) Which one of the following compounds is more easily hydrolyzed by KOH and why?

CH3CHCICH2CH3 or CH3CH2CH2Cl

(iii) Which one undergoes S N 2 substitution reaction faster and why?

1063 Views

28.

Define the following as related to proteins:

(i) Peptide linkage

(ii) Primary structure

(iii) Denaturation

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29.

Differentiate between thermoplastic and thermosetting polymers. Give one example of each.

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 Multiple Choice QuestionsLong Answer Type

30.

(a) Draw the molecular structure of the following compounds.

(i) N2O5

(ii) XeOF4

(b) Explain the following observation:

(i) Sulphur has a greater tendency for catenation than oxygen.

(ii) ICI is more reactive than I2.

(iii) Despite the lower value of its electron gain enthalpy with a negative sign, fluorine (F2) is a stronger oxidizing agent than Cl2.

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