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

Give a reason for the following: 

Actinoids show irregularities in their electronic configurations.

Give an example and suggest a reason for the following feature of the transition metal chemistry:

The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.

Account for the following:

Mn²⁺ is more stable than Fe²⁺ towards oxidation to +3 state.

Why \[\ce{HCl}\] should not be used for potassium permanganate titrations?

Account for the following:

Transition metals form alloys.

Account for the following:

Sc³⁺ is colourless whereas Ti³⁺ is coloured in an aqueous solution.

What is the reason for the stability of colloidal sols?

Define the following term:

Zeta potential

[NiCl₄]²⁻ is paramagnetic, while [Ni(CO)₄] is diamagnetic, though both are tetrahedral. Why? (Atomic number of Ni = 28)

Write one similarity between Physisorption and Chemisorption

Following compounds are given to you :

2-Bromopentane, 2-Bromo-2-methylbutane, 1-Bromopentane

1) Write the compound which is most reactive towards S_N2 reaction.

2) Write the compound which is optically active.

3)  Write the compound which is most reactive towards β-elimination reaction. 

What are Heteroleptic complexes?

How do you convert: 

2-bromobutane to but-2-ene

What is the role of coke in the extraction of iron from its oxides?

Auto-oxidation of chloroform in air and sunlight produces a poisonous gas known as ______.

Draw the structures of the following molecules: BrF₃

Write the equations involved in the following reactions : Williamson synthesis

Give simple chemical tests to distinguish between the following pairs of compounds :

Ethanol and phenol

Account for the following 

The enthalpy of atomisation is lowest for Zn in 3d series of the transition elements.

Arrange the following in the order of the property indicated against set :
H₂O, H₂S, H₂Se, H₂Te − increasing acidic character.