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# Chemistry Delhi Set 1 2012-2013 CBSE (Science) Class 12 Question Paper Solution

Chemistry [Delhi Set 1]
Marks: 70Academic Year: 2012-2013
Date: March 2013

[1]1

How many atoms constitute one unit cell of a face-centered cubic crystal?

Concept: Number of Atoms in a Unit Cell
Chapter: [1] Solid State
[1]2

Name the method used for the refining of Nickel metal.

Concept: Refining
Chapter: [6] General Principles and Processes of Isolation of Elements
[1]3

What is the covalency of nitrogen in N2O5?

Concept: Classification of Crystalline Solids
Chapter: [1] Solid State
[1]4

Write the IUPAC name of

Concept: Nomenclature of Coordination Compounds - Naming of Mononuclear Coordination Compounds
Chapter: [9] Coordination Compounds
[1]5

What happens when CH3 − Br is treated with KCN?

Concept: Chemical Reactions of Haloalkanes and Haloarenes - Reactions of Haloarenes - Nucleophilic Substitution
Chapter: [10] Haloalkanes and Haloarenes
[1]6

Write the structure of 3-methyl butanal

Concept: Aldehydes and Ketones - Nomenclature
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]7

Arrange the following in increasing order of their basic strength in aqueous solution:

CH3.NH2, (CH3)3N, (CH3)2NH

Concept: Amines - Chemical Reactions of Amines - Basic Character of Amines
Chapter: [13] Organic Compounds Containing Nitrogen
[1]8

What are three types of RNA molecules which perform different functions?

Concept: Introduction of Nucleic Acids
Chapter: [14] Biomolecules
[2]9

8 g of glucose, C6H12O6 (Molar Mass = 180 g mol−1) is dissolved in 1 kg of water in a sauce pan. At what temperature will this solution boil?

(Kb for water = 0.52 K kg mol−1, boiling point of pure water = 373.15 K)

Concept: Colligative Properties and Determination of Molar Mass - Elevation of Boiling Point
Chapter: [2] Solutions
[2]10

The conductivity of 0.20 M solution of KCl at 298 K is 0.025 S cm−1. Calculate its molar conductivity.

Concept: Conductance of Electrolytic Solutions - Variation of Conductivity and Molar Conductivity with Concentration
Chapter: [3] Electrochemistry
[2]11
[2]11.1

Write the dispersed phase and dispersion medium of the following colloidal systems:

(i) Smoke

(ii) Milk

Concept: Catalysis - Enzyme Catalysis
Chapter: [5] Surface Chemistry
[2]11.2

What are lyophilic and lyophobic colloids ? Which of these sols can be easily coagulated on the addition of small amounts of electrolytes?

Concept: Classification of Colloids - Classification Based on Nature of Interaction Between Dispersed Phase and Dispersion Medium
Chapter: [5] Surface Chemistry
[2]12

Write the differences between physisorption and chemisorption with respect to the following:

(i) Specificity

(ii) Temperature dependence

(iii) Reversibility and

(iv) Enthalpy change

Chapter: [5] Surface Chemistry
[2]13

Which solution is used for the leaching of silver metal in the presence of air in the metallurgy of silver?

Concept: Oxidation Reduction
Chapter: [6] General Principles and Processes of Isolation of Elements

Out of C and CO, which is a better reducing agent at the lower temperature range in the blast furnace to extract iron from the oxide ore?

Concept: Occurrence of Metals
Chapter: [6] General Principles and Processes of Isolation of Elements
[2]14

What happens when

(i) PCl5 is heated ? Write the reactions involved.

Concept: P - Block Group 17 Elements - Chlorine
Chapter: [7] P - Block Elements

What happens when

H3PO3 is heated ?

Write the reactions involved.

Concept: P - Block Group 15 Elements - Phosphine
Chapter: [7] P - Block Elements
[2]15

Which metal in the first transition series (3d series) exhibits + 1 oxidation state most frequently and why?

Concept: General Properties of the Transition Elements (D-block)
Chapter: [8] "D" and "F" Block Elements

Which of the following cations are coloured in aqueous solutions and why ?

Sc3+, V3+, Ti4+, Mn2+ (At. Nos. Sc = 21, V = 23, Ti = 22, Mn = 25)

Concept: General Properties of the Transition Elements (D-block)
Chapter: [8] "D" and "F" Block Elements
[2]16

Chlorobenzene is extremely less reactive towards a nucleophilic substitution reaction. Give two reasons for the same.

Concept: Chemical Reactions of Haloalkanes and Haloarenes - Reactions of Haloarenes - Nucleophilic Substitution
Chapter: [10] Haloalkanes and Haloarenes
[2]17

Explain the mechanism of the following reaction:

Concept: Preparation of Ethers from Dehydration of Alcohols and Williamson Systhesis
Chapter: [11] Alcohols, Phenols and Ethers
[2]18

How will you convert: Propene to Propan-2-ol?

Concept: Preparation of Alcohols from Alkenes, Carbonyl Compounds and Grignard Reagents
Chapter: [11] Alcohols, Phenols and Ethers

How will you convert: Phenol to 2, 4, 6 − trinitrophenol?

Concept: Preparation of Alcohols from Alkenes, Carbonyl Compounds and Grignard Reagents
Chapter: [11] Alcohols, Phenols and Ethers
[3]19

What type of semiconductor is obtained when silicon is doped with boron?

Concept: Electrical Properties - Applications of N-type and P-type Semiconductors
Chapter: [1] Solid State

What type of magnetism is shown in the following alignment of magnetic moments?

Concept: Magnetic Properties
Chapter: [1] Solid State

What type of point defect is produced when AgCl is doped with CdCl2?

Concept: Imperfections in Solids - Introduction
Chapter: [1] Solid State
[3]20

Determine the osmotic pressure of a solution prepared by dissolving 2.5 × 10−2 g of K2SO4 in 2L of water at 25°C, assuming that it is completely dissociated.

(R = 0.0821 L atm K−1 mol−1, Molar mass of K2SO4 = 174 g mol−1)

Concept: Colligative Properties and Determination of Molar Mass - Osmosis and Osmotic Pressure
Chapter: [2] Solutions
[3]21

Calculate the emf of the following cell at 298 K:

Fe(s)|Fe^(2+)(0.001M)||H^+(1M)|H_2 "(g)(1bar) ",Pt(s)

("Given " E_(cell)^@=+0.44V)

Concept: Galvanic Cells - Introduction
Chapter: [3] Electrochemistry
[3]22 | Attempt any one of the following
[3]22.1

How would you account for the following?

Transition metals exhibit variable oxidation states.

Concept: General Properties of the Transition Elements (D-block)
Chapter: [8] "D" and "F" Block Elements

How would you account for the following?

Zr (Z = 40) and Hf (Z = 72) have almost identical radii.

Concept: General Properties of the Transition Elements (D-block)
Chapter: [8] "D" and "F" Block Elements

How would you account for the following?

Transition metals and their compounds act as catalyst.

Concept: General Properties of the Transition Elements (D-block)
Chapter: [8] "D" and "F" Block Elements
[3]22.2

Complete the following chemical equations:

(i) Cr_2O_7^(2-)+6Fe^(2+)+14H^+ ->

(ii) 2CrO_4^(2-)+2H^+ ->

(iii) 2MnO_4^-+5C_2O_4^(2-)+16H^+ ->

Concept: General Properties of the Transition Elements (D-block)
Chapter: [8] "D" and "F" Block Elements
[3]23

Write the IUPAC names of the following coordination compounds: [Cr(NH3)3Cl3]

Concept: Nomenclature of Coordination Compounds - Naming of Mononuclear Coordination Compounds
Chapter: [9] Coordination Compounds

Write the IUPAC names of the following coordination compounds:  K3[Fe(CN)6]

Concept: Nomenclature of Coordination Compounds - Naming of Mononuclear Coordination Compounds
Chapter: [9] Coordination Compounds

Write the IUPAC names of the following coordination compounds:

[CoBr2(en)2]+, (en = ethylenediamine)

Concept: Nomenclature of Coordination Compounds - Naming of Mononuclear Coordination Compounds
Chapter: [9] Coordination Compounds
[3]24

Give the structures of A, B and C in the following reactions:

Concept: Diazonium Salts - Chemical Reaction of Diazonium Salts - Reactions Involving Displacement of Nitrogen
Chapter: [13] Organic Compounds Containing Nitrogen

Give the structures of A, B and C in the following reaction:

Concept: Diazonium Salts - Chemical Reaction of Diazonium Salts - Reactions Involving Displacement of Nitrogen
Chapter: [13] Organic Compounds Containing Nitrogen
[3]25
[1]25.1

Write the names and structure of the monomers of the following polymers: Buna − S

Concept: Introduction of Polymers
Chapter: [15] Polymers
[1]25.2

Write the names and structure of the monomers of the following polymers: Neoprene

Concept: Introduction of Polymers
Chapter: [15] Polymers
[1]25.3

Write the names and structure of the monomers of the following polymers: Nylon-6, 6

Concept: Types of Polymerisation Reactions - Condensation Polymerisation Or Step Growth Polymerisation
Chapter: [15] Polymers
[3]26

After watching a programme on TV about the adverse effects of junk food and soft drinks on the health of school children, Sonali, a student of Class XII, discussed the issue with the school principal. Principal immediately instructed the canteen contractor to replace the fast food with the fibre and vitamins rich food like sprouts, salad, fruits etc. This decision was welcomed by the parents and the students.

After reading the above passage, answer the following questions:

(a) What value are expressed by Sonali and the Principal of the school?

(b) Give two examples of water-soluble vitamins.

Concept: Introduction of Vitamins
Chapter: [14] Biomolecules
[3]27

Which one of the following is a food preservative?

Equanil, Morphine, Sodium benzoate

Concept: Chemicals in Food - Artificial Sweetening Agents and Food Preservatives
Chapter: [16] Chemistry in Everyday Life

Why is bithional added to soap?

Concept: Cleansing Agents - Soaps
Chapter: [16] Chemistry in Everyday Life

What use of drugs is used in sleeping pills?

Concept: Drugs and Their Classification
Chapter: [16] Chemistry in Everyday Life
[5]28 | Attempt any one of the following
[5]28.1

A reaction is second order in A and first order in B.

(i) Write the differential rate equation.

(ii) How is the rate affected on increasing the concentration of A three times?

(iii) How is the rate affected when the concentrations of both A and B are doubled?

Concept: Factors Influencing Rate of a Reaction
Chapter: [4] Chemical Kinetics

A first order reaction takes 40 minutes for 30% decomposition. Calculate t1/2 for this reaction. (Given log 1.428 = 0.1548)

Concept: Integrated Rate Equations - Half-life of a Reaction
Chapter: [4] Chemical Kinetics
[5]28.2

For a first order reaction, show that time required for 99% completion is twice the time required for the completion of 90% of reaction.

Concept: Integrated Rate Equations - Half-life of a Reaction
Chapter: [4] Chemical Kinetics

(b) Rate constant ‘k’ of a reaction varies with temperature ‘T’ according to the equation:

logk=logA-E_a/2.303R(1/T)

Where Ea is the activation energy. When a graph is plotted for logk Vs. 1/T a straight line with a slope of −4250 K is obtained. Calculate ‘Ea’ for the reaction.(R = 8.314 JK−1 mol−1)

Concept: Temperature Dependence of the Rate of a Reaction
Chapter: [4] Chemical Kinetics
[5]29 | Attempt any one of the following
[5]29.1
[3]29.1.1

Give reasons for the following:

(i) Bond enthalpy of F2 is lower than that of Cl2.

(ii) PH3 has lower boiling point than NH3.

Concept: Bonding in Coordination Compounds - Introduction
Chapter: [9] Coordination Compounds
[3]29.1.2

Draw the structures of the following molecules: XeF4

Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
Chapter: [7] P - Block Elements

Draw the structures of the following molecules: BrF3

Concept: P - Block Group 17 Elements - Interhalogen Compounds
Chapter: [7] P - Block Elements

Draw the structures of the following molecules: (HPO3)3

Concept: P - Block Group 15 Elements - Compounds of Phosphorus
Chapter: [7] P - Block Elements
[5]29.2
[3]29.2.1

Account for the following:

Helium is used in diving apparatus.

Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
Chapter: [7] P - Block Elements

Account for the following: Fluorine does not exhibit positive oxidation state.

Concept: P - Block Group 17 Elements - Concept of Group 17 Elements
Chapter: [7] P - Block Elements

Account for the following: Oxygen shows catenation behavior less than sulphur.

Concept: Concept of Group 16 Elements
Chapter: [7] P - Block Elements
[3]29.2.2

Draw the structures of the following molecules: XeF2

Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
Chapter: [7] P - Block Elements

Draw the structures of the following molecules: H2S2O8

Concept: P - Block Group 16 Elements - Oxoacids of Sulphur
Chapter: [7] P - Block Elements
[5]30 | Attempt any one of the following
[5]30.1
[3]30.1.1

Although phenoxide ion has more number of resonating structures than Carboxylate ion, Carboxylic acid is a stronger acid than phenol. Give two reasons.

Concept: Carboxylic Acids - Chemical Reactions of Carboxylic Acids - Reactions Involving Cleavege of O-H Bond
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[2]30.1.2

How will you bring about the following conversions?

Propanone to propane

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Reduction
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids

How will you bring about the following conversion?

Benzoyl chloride to benzaldehyde

Concept: Aldehydes and Ketones - Preparation of Aldehydes
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids

How will you bring about the following conversion?

Ethanal to but-2-enal

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Reactions Due to A-hydrogen
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[5]30.2
[3]30.2.1

Complete the following reactions:

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Other Reactions
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids

Complete the following reactions:

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Other Reactions
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids

Complete the following reactions:

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Other Reactions
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[2]30.2.2

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

Ethanal and Propanal

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Oxidation
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids

Give simple chemical tests to distinguish between the following pairs of compounds:  Benzoic acid and Phenol

Concept: Chemical Reactions of Phenols (Only)
Chapter: [11] Alcohols, Phenols and Ethers

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## CBSE previous year question papers Class 12 Chemistry with solutions 2012 - 2013

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