Science (English Medium) कक्षा १२ - CBSE Important Questions

Account for the following:

Mn shows the highest oxidation state of +7 with oxygen but with fluorine, it shows oxidation state of +4.

Account for the following:

Cu⁺² salts are coloured, while Zn²⁺ salts are white.

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

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