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CBSE (Science) Class 12 - CBSE Important Questions for Chemistry

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Chemistry
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Draw the structures of the following molecules: XeF4

Appears in 23 question papers
Chapter: [0.07] P - Block Elements
Concept: P - Block Group 18 Elements > Concept of Group 18 Elements

Define terms: Fuel cell

Appears in 13 question papers
Chapter: [0.03] Electrochemistry
Concept: Batteries > Primary Batteries

Write the chemical equations involved in the following reactions:(i) Hoffmann-bromamide degradation reaction

Appears in 12 question papers
Chapter: [0.13] Organic Compounds Containing Nitrogen
Concept: Amines > Preparation of Amines

Amino acids show amphoteric behaviour. Why?

Appears in 11 question papers
Chapter: [0.14] Biomolecules
Concept: Proteins > Amino Acids

How do you convert the Toluene to Benzoic acid

Appears in 10 question papers
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids
Concept: Acids > Nomenclature of Carboxylic Acids

Illustrate the following reaction giving suitable example in each case:Gabriel phthalimide synthesis

Appears in 10 question papers
Chapter: [0.13] Organic Compounds Containing Nitrogen
Concept: Amines > Preparation of Amines

Define the following terms: Essential amino acids

Appears in 10 question papers
Chapter: [0.14] Biomolecules
Concept: Proteins > Amino Acids

Why is bithional added to soap?

Appears in 10 question papers
Chapter: [0.16] Chemistry in Everyday Life
Concept: Cleansing Agents - Soaps

An element 'X' (At. mass = 40 g mol-1) having f.c.c. the structure has unit cell edge length of 400 pm. Calculate the density of 'X' and the number of unit cells in 4 g of 'X'. (NA = 6.022 × 1023 mol-1)

Appears in 9 question papers
Chapter: [0.01] Solid State
Concept: Number of Atoms in a Unit Cell

Calculate the freezing point of a solution containing 60 g of glucose (Molar mass = 180 g mol–1) in 250 g of water. (Kf of water = 1.86 K kg mol–1)

Appears in 9 question papers
Chapter: [0.02] Solutions
Concept: Colligative Properties and Determination of Molar Mass > Depression of Freezing Point

Give reasons for the following:

Measurement of osmotic pressure method is preferred for the determination of molar masses of macromolecules such as proteins and polymers.

Appears in 9 question papers
Chapter: [0.02] Solutions
Concept: Colligative Properties and Determination of Molar Mass > Depression of Freezing Point

Give reasons for the following :

Aquatic animals are more comfortable in the cold water than in warm water.

Appears in 9 question papers
Chapter: [0.02] Solutions
Concept: Solubility > Solubility of a Gas in a Liquid

Give reasons for the following

Elevation of the boiling point of 1 M KCl solution is nearly double than that of 1 M sugar solution.

Appears in 9 question papers
Chapter: [0.02] Solutions
Concept: Abnormal Molar Masses

Write the cell reaction and calculate the e.m.f of the following cell at 298 K:

`Sn(s) | Sn^(2+) (0.004 M) || H^(+) (0.020 M) | H_2 (g) ("1 bar") | Pt(s)`

(Given: `E_(Sn^(2+)"/"Sn)^0 = -0.14` V)

Appears in 9 question papers
Chapter: [0.03] Electrochemistry
Concept: Galvanic Cells - Measurement of Electrode Potential

Give reasons On the basis of E° values, O2 gas should be liberated at anode but it is Cl2 gas which is liberated in the electrolysis of aqueous NaCl.

Appears in 9 question papers
Chapter: [0.03] Electrochemistry
Concept: Conductance of Electrolytic Solutions > Measurement of the Conductivity of Ionic Solutions

Give reasons Conductivity of CH3COOH decreases on dilution.

Appears in 9 question papers
Chapter: [0.03] Electrochemistry
Concept: Conductance of Electrolytic Solutions > Measurement of the Conductivity of Ionic Solutions

For the reaction

`2AgCl (s) + H_2 (g) ("1 atm") -> 2Ag (s) + 2H^(+)  (0.1 M) +  2Cl^(-) (0.1 M)`

`triangleG^0 = -43600 J at 25^@ C`

Calculate the e.m.f. of the cell

`[log 10^(-n) = -n]` 

Appears in 9 question papers
Chapter: [0.03] Electrochemistry
Concept: Relation Between Gibbs Energy Change and Emf of a Cell

Write two advantages of fuel cell

Appears in 9 question papers
Chapter: [0.03] Electrochemistry
Concept: Fuel Cells

For the reaction 

2N2O5 (g) → 4NO2 (g) + O2 (g), the rate of formation of NO2 (g) is 2·8 × 10–3 M s–1. Calculate the rate of disappearance of N2O5 (g).

Appears in 9 question papers
Chapter: [0.04] Chemical Kinetics
Concept: Rate of a Chemical Reaction

A first-order reaction is 50% completed in 40 minutes at 300 K and in 20 minutes at 320 K. Calculate the activation energy of the reaction. (Given : log 2 = 0·3010, log 4 = 0·6021, R = 8·314 JK–1 mol–1)

Appears in 9 question papers
Chapter: [0.04] Chemical Kinetics
Concept: Temperature Dependence of the Rate of a Reaction
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