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Science (English Medium) Class 12 - CBSE Important Questions

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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?

Appears in 4 question papers
Chapter: [3] Chemical Kinetics
Concept: Factors Influencing Rate of a Reaction

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.

Appears in 4 question papers
Chapter: [3] Chemical Kinetics
Concept: Factors Influencing Rate of a Reaction

A first-order reaction is 50% complete in 30 minutes at 300 K and in 10 minutes at 320 K. Calculate activation energy (Ea) for the reaction. [R = 8.314 J K−1 mol−1]

[Given: log 2 = 0.3010, log 3 = 0.4771, log 4 = 0.6021]

Appears in 4 question papers
Chapter: [3] Chemical Kinetics
Concept: Temperature Dependence of the Rate of a Reaction

Account for the following:

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

Appears in 4 question papers
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

Account for the following:

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

Appears in 4 question papers
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

Give a reason for the following: 

Actinoids show irregularities in their electronic configurations.

Appears in 4 question papers
Chapter: [4] d-block and f-block Elements
Concept: F-block Elements >> The Actinoids

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.

Appears in 4 question papers
Chapter: [4] d-block and f-block Elements
Concept: Important Compounds of Transition Elements

Account for the following:

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

Appears in 4 question papers
Chapter: [4] d-block and f-block Elements
Concept: Electronic Configurations of the d-block Elements

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

Appears in 4 question papers
Chapter: [4] d-block and f-block Elements
Concept: Important Compounds of Transition Elements

Account for the following:

Transition metals form alloys.

Appears in 4 question papers
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

Account for the following:

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

Appears in 4 question papers
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

What is the reason for the stability of colloidal sols?

Appears in 4 question papers
Chapter: [5] Surface Chemistry
Concept: Properties of Colloidal Solutions

Define the following term:

Zeta potential

Appears in 4 question papers
Chapter: [5] Surface Chemistry
Concept: Properties of Colloidal Solutions

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

Appears in 4 question papers
Chapter: [5] Coordination Compounds
Concept: Bonding in Coordination Compounds >> Valence Bond Theory (VBT)

Write one similarity between Physisorption and Chemisorption

Appears in 4 question papers
Chapter: [5] Surface Chemistry
Concept: Types of Adsorption

Following compounds are given to you :

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

1) Write the compound which is most reactive towards SN2 reaction.

2) Write the compound which is optically active.

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

Appears in 4 question papers
Chapter: [5] Coordination Compounds
Concept: Important Terms Pertaining to Coordination Compounds

What are Heteroleptic complexes?

Appears in 4 question papers
Chapter: [5] Coordination Compounds
Concept: Important Terms Pertaining to Coordination Compounds

How do you convert: 

2-bromobutane to but-2-ene

Appears in 4 question papers
Chapter: [6] Haloalkanes and Haloarenes
Concept: Reactions of Haloalkanes - Elimination Reactions

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

Appears in 4 question papers
Chapter: [6] General Principles and Processes of Isolation of Elements
Concept: Occurrence of Metals

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

Appears in 4 question papers
Chapter: [6] Haloalkanes and Haloarenes
Concept: Polyhalogen Compounds
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