Science (English Medium) कक्षा १२ - CBSE Question Bank Solutions for Chemistry

What should be the considerations during the extraction of metals by electrochemical method?

Which of the following acids forms three series of salts?

Phosphorus forms a number of oxoacids. Out of these oxoacids phosphinic acid has strong reducing property. Write its structure and also write a reaction showing its reducing behaviour.

Which of the following statements are correct about the reaction intermediate?

(i) Intermediate (c) is unstable because in this carbon is attached to 5 atoms.

(ii) Intermediate (c) is unstable because carbon atom is sp² hybridised.

(iii) Intermediate (c) is stable because carbon atom is sp² hybridised.

(iv) Intermediate (c) is less stable than the reactant (b).

Draw other resonance structures related to the following structure and find out whether the functional group present in the molecule is ortho, para directing or meta directing.

Why is it necessary to avoid even traces of moisture during the use of a Grignard reagent?

The process of converting alkyl halides into alcohols involves ______.

Mark the correct increasing order of reactivity of the following compounds with HBr/HCl.

(a)
(b)
(c)

Name the factors responsible for the solubility of alcohols in water.

Suggest a reagent for the following conversion.

Alcohols react with active metals e.g. Na, K etc. to give corresponding alkoxides. Write down the decreasing order of reactivity of sodium metal towards primary, secondary and tertiary alcohols.

Explain why is OH group in phenols more strongly held as compared to OH group in alcohols.

Explain why nucleophilic substitution reactions are not very common in phenols.

In Kolbe’s reaction, instead of phenol, phenoxide ion is treated with carbon dioxide. Why?

Ethers can be prepared by Williamson synthesis in which an alkyl halide is reacted with sodium alkoxide. Di-tert-butyl ether can’t be prepared by this method. Explain.

Why is the C – O – H bond angle in alcohols slightly less than the tetrahedral angle whereas the C – O – C bond angle in ether is slightly greater?

Assertion: Bond angle in ethers is slightly less than the tetrahedral angle.

Reason: There is a repulsion between the two bulky (–R) groups.

The gas evolved when methylamine reacts with nitrous acid is:

Acid anhydrides on reaction with primary amines give ______.

Carbohydrates are essential for life in both plants and animals. Name the carbohydrates that are used as storage molecules in plants and animals, also name the carbohydrate which is present in wood or in the fibre of cotton cloth.