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

Explain the fact that in aryl alkyl ethers 

1. the alkoxy group activates the benzene ring towards electrophilic substitution and
2. it directs the incoming substituents to ortho and para positions in the benzene ring.

Write the mechanism of the reaction of HI with methoxymethane.

Why does O₃ act as a powerful oxidising agent?

How is O₃ estimated quantitatively?

Which aerosols deplete ozone?

Write the product(s) in the following reaction

Write the formula of reagents used in the following reactions :

Bromination of phenol to 2,4,6-tribromophenol

Write the formula of reagents used in the following reactions :

Hydroboration of propene and then oxidation to propanol.

What happens when CdCl₂ is doped with AgCl?

Calculate the freezing point of a solution containing 60 g of glucose (Molar mass = 180 g mol^–1) in 250 g of water. (K_f of water = 1.86 K kg mol^–1)

Account for the following:

pK_a value of 4-nitrobenzoic acid is lower than that of benzoic acid.

Give reasons for the following:

Measurement of osmotic pressure method is preferred for the determination of molar masses of macromolecules such as proteins and polymers.

(A), (B) and (C) are three non-cyclic functional isomers of a carbonyl compound with molecular formula C₄H₈O. Isomers (A) and (C) give positive Tollens' test whereas isomer (B) does not give Tollens' test but gives positive Iodoform test. Isomers (A) and (B) on reduction with Zn(Hg)/conc. HCl give the same product (D).

1) Write the structures of (A), (B), (C) and (D).

2) Out of (A), (B), and (C) isomers, which one is least reactive towards the addition of HCN?

Write the structures of the main products in the following reactions :

Define the following with an example

Denatured protein

Write two advantages of fuel cell

Give reason Aromatic diazonium salts are more stable than aliphatic diazonium salts.

Why are alkyl halides insoluble in water?

The two O−O bond lengths in the ozone molecule are equal.

 What happens when AgCl is doped with 2? CdCl What is the name of this defect?