Science (English Medium) इयत्ता १२ - CBSE Important Questions for Chemistry

Among the following, which one acts as a food preservative?

Aspartame, Aspirin, Sodium Benzoate, Paracetamol

How do you convert the following:

Aniline to phenol

How do you convert the Ethanal to Propanone

When concentrated sulphuric acid was added to an unknown salt present in a test tube a brown gas (A) was evolved. This gas intensified when copper turnings were added to this test tube. On cooling, the gas (A) changed into a colourless solid (B).

1) Identify (A) and (B).

2) Write the structures of (A) and (B).

3) Why does gas (A) change to solid on cooling?

Arrange the following in the decreasing order of their reducing character :

HF, HCl, HBr, HI

Account for the following:

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

Give a simple chemical test to distinguish between Aniline and N, N-dimethylaniline

What type of azeotrope is formed by positive deviation from Raoult’s law?

Define the following term:

Fuel cell

How would you account for the following: Transition metals form complex compounds.

Account for the following:

E° value for the Mn³⁺/Mn²⁺ couple is much more positive than that for Cr³⁺/Cr²⁺.

Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.

Give reason for the following:

The transition metals generally form coloured compounds.

On the basis of crystal field theory, write the electronic configuration for d⁴ ion if ∆₀ < P.

Explain the following reaction:

Wolff-Kishner reduction

Explain the following reaction:

Cannizzaro reaction

Write chemical test to distinguish between the following compounds:

Phenol and Benzoic acid

Why vitamin C cannot be stored in our body?

Define azeotropes. 

What type of deviation is shown by a mixture of ethanol and acetone? Give reason.