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

Show that the time required for 99% completion is double of the time required for the completion of 90% reaction.

How would you account for the following:

The chemistry of actinoids is more complicated as compared to lanthanoids.

Give reasons for the following:

The transition metals generally form coloured compounds.

Define coagulation.

Name the method of refining of metals such as Germanium.

What is the role of silica in the extraction of copper?

Give simple chemical tests to distinguish between the following pairs of compounds:  Benzoic acid and Phenol

How do you convert the following :
Phenol to anisole

Write the structures of the following molecules: XeOF₄

Write the mechanism of the following reaction :

Why vitamin C cannot be stored in our body?

Explain the term Antiseptics

Define azeotropes. 

Calculate the number of unit cells in 8.1 g of aluminium if it crystallizes in a f.c.c. structure. (Atomic mass of Al = 27 g mol^–1)

Give reasons:Ferrimagnetic substances show better magnetism than antiferromagnetic substances.

Define the term: 

Ideal solution

What type of azeotrope is formed by positive deviation from Raoult's law ? Give an example.

Calculate the e.m.f. of the following cell at 298 K:

Fe(s) | Fe²⁺ (0.001 M) | | H⁺ (0.01 M) | H₂(g) (1 bar) | Pt(s)

Given that \[\ce{E^0_{cell}}\] = 0.44 V

[log 2 = 0.3010, log 3 = 0.4771, log 10 = 1]

Calculate emf of the following cell at 25°C:

\[\ce{Sn/Sn^2+ (0.001 M) || H+ (0.01 M) | H2_{(g)} (1 bar) | Pt_{(s)}}\]

Given: \[\ce{E^\circ(Sn^2+/sn) = -0.14 V, E^\circ H+/H2 = 0.00 V (log 10 = 1)}\]

Account for the following:

E° value for the Mn³⁺/Mn²⁺ couple is highly positive (+1.57 V) as compare to Cr³⁺/Cr²⁺.