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

Define the following term:

Fuel cell

Which of the following cell was used in the Apollo space programme?

For a reaction A + B ⟶ P, the rate is given by

Rate = k [A] [B]²

How is the rate of reaction affected if the concentration of B is doubled?

For a reaction A + B ⟶ P, the rate is given by

Rate = k [A] [B]²

What is the overall order of reaction if A is present in large excess?

For a chemical reaction R → P, the variation in the concentration (R) vs. time (t) plot is given as:

(i) Predict the order of the reaction.

(ii) What is the slope of the curve ?

(iii) Write the unit of rate constant for this reaction.

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.

Account for the following :

Zn is not considered as a transition element.

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?

Write any two consequences of Lanthanoid Contraction.

Give reasons for the following statement:

\[\ce{Zn}\], \[\ce{Cd}\] and \[\ce{Hg}\] are soft metals.

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