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

Illustrate Sandmeyer's reaction with an equation.

What type of semiconductor is obtained when silicon is doped with boron? 

After watching a programme on TV about the adverse effects of junk food and soft drinks on the health of school children, Sonali, a student of Class XII, discussed the issue with the school principal. Principal immediately instructed the canteen contractor to replace the fast food with the fibre and vitamins rich food like sprouts, salad, fruits etc. This decision was welcomed by the parents and the students. 

After reading the above passage, answer the following questions:

(a) What value are expressed by Sonali and the Principal of the school?

(b) Give two examples of water-soluble vitamins.

Although phenoxide ion has more number of resonating structures than carboxylate ion, carboxylic acid is a stronger acid than phenol. Give two reasons.

Give reasons for the following observations: Addition of alum purifies the water

Write the name of the vitamin responsible for the coagulation of blood.

Write the conditions to maximize the yield of H₂SO₄ by contact process.

Why pKa of F-CH₂-COOH is lower than that of Cl−CH₂−COOH?

Write the name of vitamin whose deficiency causes bone deformities in children.

Distinguish between the following : Benzoic acid and methyl benzoate

What are emulsions?

What are the different types of emulsions? Give one example of each type.

Complete the following equations: CaF₂+H₂SO₄ →

What are the dispersed phase and dispersion medium in milk?

Complete the following equations: C + conc. H₂SO₄ →

Draw the structure of the following:

H₂SO₄

How do emulsifires stabilise emulsion? Name two emulsifiers.

Action of soap is due to emulsification and micelle formation. Comment.

Give four uses of emulsions.

Write a short note on the following:

Coupling reaction