# Chemistry Delhi Set 2 2014-2015 CBSE (Science) Class 12 Question Paper Solution

Chemistry [Delhi Set 2]
Date: March 2015

[1] 1

Which would undergo SN2 reaction faster in the following pair and why ?

Concept: Hydrocarbons: Alkanes - Reactions of Haloalkanes - Nucleophilic Substitution Reactions
Chapter: [0.1] Haloalkanes and Haloarenes
[1] 2

Out of BaCl2 and KCl, which one is more effective in causing coagulation of a negatively charged colloidal Sol? Give reason.

Concept: Properties of Colloidal Solutions
Chapter: [0.05] Surface Chemistry
[1] 3

What is the formula of a compound in which the element Y forms ccp lattice and atoms of X occupy 1/3rd of tetrahedral voids?

Concept: Crystal Lattices and Unit Cells - Introduction
Chapter: [0.01] Solid State
[1] 4

What is the basicity of H3PO4 ?

Concept: P - Block Group 15 Elements - Compounds of Phosphorus
Chapter: [0.07] P - Block Elements
[1] 5

Write the IUPAC name of the given compound :

Concept: Nomenclature of Coordination Compounds - Naming of Mononuclear Coordination Compounds
Chapter: [0.09] Coordination Compounds
[2] 6
[1] 6.1

Name the reagents used in the following reactions:

Concept: Preparation of Alcohols from Alkenes, Carbonyl Compounds and Grignard Reagents
Chapter: [0.11] Alcohols, Phenols and Ethers
[1] 6.2

Name the reagents used in the following reactions:

Concept: Acids - Methods of Preparation of Carboxylic Acids
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids
[2] 7 | Attempt any ONE
[2] 7.1

What is meant by positive deviations from Raoult's law? Give an example. What is the sign of ∆mixH for positive deviation?

Concept: Vapour Pressure of Liquid - Vapour Pressure of Liquid- Liquid Solutions
Chapter: [0.02] Solutions
[2] 7.2

Define azeotropes.

Concept: Vapour Pressure of Liquid - Vapour Pressure of Liquid- Liquid Solutions
Chapter: [0.02] Solutions

What type of azeotrope is formed by positive deviation from Raoult's law ? Give an example.

Concept: Vapour Pressure of Liquid - Vapour Pressure of Liquid- Liquid Solutions
Chapter: [0.02] Solutions
[2] 8
[1] 8.1

Following reactions occur at cathode during the electrolysis of aqueous silver chloride solution :

Ag^+(aq)+e^(-)rarrAg(s)" ""      ""       "E^@=+0.80V

H^+(aq)+e^(-)rarr1/2H_2(g)" "" "" " E^@=0.00V

On the basis of their standard reduction electrode potential (E°) values, which reaction is feasible at the cathode and why ?

Concept: Relation Between Gibbs Energy Change and Emf of a Cell
Chapter: [0.03] Electrochemistry
[1] 8.2

Define limiting molar conductivity.

Concept: Conductance of Electrolytic Solutions - Variation of Conductivity and Molar Conductivity with Concentration
Chapter: [0.03] Electrochemistry

Why conductivity of an electrolyte solution decreases with the decrease in concentration ?

Concept: Conductance of Electrolytic Solutions - Variation of Conductivity and Molar Conductivity with Concentration
Chapter: [0.03] Electrochemistry
[2] 9

What are the transition elements? Write two characteristics of the transition elements.

Concept: General Properties of the Transition Elements (D-block)
Chapter: [0.08] "D" and "F" Block Elements
[2] 10
[1] 10.1

Write down the IUPAC name of the following complex: [Cr(NH3)2Cl2(en)]Cl (en = ethylenediamine)

Concept: Nomenclature of Coordination Compounds - Naming of Mononuclear Coordination Compounds
Chapter: [0.09] Coordination Compounds
[1] 10.2

Write the formula for the following complex:

Pentaamminenitrito-o-Cobalt (III).

Concept: Nomenclature of Coordination Compounds - Formulas of Mononuclear Coordination Entities
Chapter: [0.09] Coordination Compounds
[2] 11
[1] 11.1

Draw the geometrical isomers of complex [Pt(NH3)2Cl2].

Concept: Isomerism in Coordination Compounds - Stereoisomerism
Chapter: [0.09] Coordination Compounds
[1] 11.2

On the basis of crystal field theory, write the electronic configuration for d4 ion if ∆0 < P.

Concept: Bonding in Coordination Compounds - Crystal Field Theory (CFT)
Chapter: [0.09] Coordination Compounds
[1] 11.3

Write the hybridization and magnetic behaviour of the complex [Ni(CO)4].

(At.no. of Ni = 28)

Concept: Bonding in Coordination Compounds - Magnetic Properties of Coordination Compounds
Chapter: [0.09] Coordination Compounds
[3] 12

Calculate emf of the following cell at 25 °C :

Fe|Fe2+(0.001 M)| |H+(0.01 M)|H2(g) (1 bar)|Pt (s)

E°(Fe2+| Fe)0.44 V E°(H+ | H20.00 V

Concept: Galvanic Cells - Introduction
Chapter: [0.03] Electrochemistry
[3] 13
[1] 13.1

Give reasons for the following observations: Leather gets hardened after tanning.

Concept: Properties of Colloidal Solutions
Chapter: [0.05] Surface Chemistry
[1] 13.2

Give reasons for the following observations: Lyophilic sol is more stable than lyophobic sol.

Concept: Classification of Colloids - Classification Based on Nature of Interaction Between Dispersed Phase and Dispersion Medium
Chapter: [0.05] Surface Chemistry
[1] 13.3

It is necessary to remove CO when ammonia is prepared by Haber's process.

Concept: Catalysis - Enzyme Catalysis
Chapter: [0.05] Surface Chemistry
[3] 14

Write the names and structures of the monomers of the following polymers

(i) Nylon-6, 6

(ii) PHBV

(iii) Neoprene

Concept: Introduction of Polymers
Chapter: [0.15] Polymers
[3] 15
[1] 15.1

Predict the products of the following reactions :

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Reduction
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids
[1] 15.2

Predict the products of the following reactions :

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Oxidation
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids
[1] 15.3

Predict the products of the following reactions :

Concept: Acids - Chemical Reactions of Carboxylic Acids - Reactions Involving –COOH Group
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids
[3] 16 | Attempt any ONE
[3] 16.1
[1] 16.1.1

How do you convert the following :
Phenol to anisole

Concept: Preparation of Ethers from Dehydration of Alcohols and Williamson Systhesis
Chapter: [0.11] Alcohols, Phenols and Ethers
[1] 16.1.2

How do you convert the following : Propan-2-ol to 2-methylpropan-2-ol

Concept: Preparation of Alcohols from Alkenes, Carbonyl Compounds and Grignard Reagents
Chapter: [0.11] Alcohols, Phenols and Ethers
[1] 16.1.3

How do you convert the following : Aniline to phenol

Concept: Preparation of Phenols from Haloarenes, Benzenesulphonic Acid, Diazonium Salts and Cumene
Chapter: [0.11] Alcohols, Phenols and Ethers
[3] 16.2
[2] 16.2.1

Write the mechanism of the following reaction :

Concept: Chemical Reactions of Alcohols and Phenols - Reactions Involving Cleavage of Carbon–Oxygen (C–O) Bond in Alcohols
Chapter: [0.11] Alcohols, Phenols and Ethers
[1] 16.2.2

Write the equation involved in the acetylation of Salicylic acid.

Concept: Chemical Reactions of Alcohols and Phenols - Reactions Involving Cleavage of O–H Bond
Chapter: [0.11] Alcohols, Phenols and Ethers
[3] 17
[1] 17.1

Which one of the following is a disaccharide : Starch, Maltose, Fructose, Glucose ?

Concept: Carbohydrates - Oligosaccharides
Chapter: [0.14] Biomolecules
[1] 17.2

What is the difference between fibrous protein and globular protein ?

Concept: Introduction of Proteins
Chapter: [0.14] Biomolecules
[1] 17.3

Write the name of vitamin whose deficiency causes bone deformities in children.

Concept: Introduction of Vitamins
Chapter: [0.14] Biomolecules
[3] 18
[1] 18.1

Give reasons : n-Butyl bromide has higher boiling point than t-butyl bromide.

Concept: Physical Properties of Haloalkanes and Haloarenes
Chapter: [0.1] Haloalkanes and Haloarenes
[1] 18.2

Give reasons : Racemic mixture is optically inactive.

Concept: Haloalkanes - R-s and D-l Configuration
Chapter: [0.1] Haloalkanes and Haloarenes
[1] 18.3

The presence of nitro group (−NO2) at o/p positions increases the reactivity of haloarenes towards nucleophilic substitution reactions.

Concept: Hydrocarbons: Alkanes - Reactions of Haloarenes - Nucleophilic Substitution
Chapter: [0.1] Haloalkanes and Haloarenes
[3] 19

3.9 g of benzoic acid dissolved in 49 g of benzene shows a depression in freezing point of 1.62 K. Calculate the van't Hoff factor and predict the nature of solute (associated or dissociated).

(Given : Molar mass of benzoic acid = 122 g mol−1, Kf for benzene = 4.9 K kg mol−1)

Concept: Abnormal Molar Masses
Chapter: [0.02] Solutions
[3] 20
[1] 20.1

Indicate the principle behind the method used for the refining of zinc.

Concept: Occurrence of Metals
Chapter: [0.06] General Principles and Processes of Isolation of Elements
[1] 20.2

What is the role of silica in the extraction of copper?

Concept: Occurrence of Metals
Chapter: [0.06] General Principles and Processes of Isolation of Elements
[1] 20.3

Which form of the iron is the purest form of commercial iron?

Concept: Occurrence of Metals
Chapter: [0.06] General Principles and Processes of Isolation of Elements
[3] 21

An element with molar mass 27 g mol−1 forms a cubic unit cell with edge length 4.05 ✕ 10−8 cm. If its density is 2.7 g cm−3, what is the nature of the cubic unit cell?

Concept: Number of Atoms in a Unit Cell
Chapter: [0.01] Solid State
[3] 22
[2] 22.1
[1] 22.1.1

How would you account for the following : Actinoid contraction is greater than lanthanoid contraction.

Concept: F-block Elements - The Actinoids
Chapter: [0.08] "D" and "F" Block Elements
[1] 22.1.2

How would you account for the following : Transition metals form coloured compounds

Concept: General Properties of the Transition Elements (D-block)
Chapter: [0.08] "D" and "F" Block Elements
[1] 22.2

Complete the following equation :

2MnO_4^(-)+6H^++5NO_2^(-)rarr

Concept: Some Important Compounds of Transition Elements - Oxides and Oxoanions of Metals
Chapter: [0.08] "D" and "F" Block Elements
[4] 23

Mr. Roy, the principal of one reputed school organized a seminar in which he invited parents and principals to discuss the serious issue of diabetes and depression in students. They all resolved this issue by strictly banning the junk food in schools and to introduce healthy snacks and drinks like soup, lassi, milk etc. in school canteens. They also decided to make compulsory half an hour physical activities for the students in the morning assembly daily. After six months, Mr. Roy conducted the health survey in most of the schools and discovered a tremendous improvement in the health of students.

(i) What are the values (at least two) displayed by Mr. Roy ?

(iii) What are tranquillizers ? Give an example.

(iv) Why is use of aspartame limited to cold foods and drinks ?

Concept: Chemicals in Food - Artificial Sweetening Agents and Food Preservatives
Chapter: [0.16] Chemistry in Everyday Life
[5] 24 | Attempt any ONE
[5] 24.1

An aromatic compound 'A' of molecular formula C7H7ON undergoes a series of reactions as shown below. Write the structures of A, B, C, D and E in the following reactions :

Concept: Amines - Preparation of Amines
Chapter: [0.13] Organic Compounds Containing Nitrogen
[5] 24.2
[3] 24.2.1
[1] 24.2.1.1

Write the structures of main products when aniline reacts with the following reagents :

Br2 water

Concept: Amines - Chemical Reactions of Amines - Electrophilic Substitution
Chapter: [0.13] Organic Compounds Containing Nitrogen
[1] 24.2.1.2

Write the structures of main products when aniline reacts with the following reagents : HCl

Concept: Amines - Chemical Reactions of Amines - Basic Character of Amines
Chapter: [0.13] Organic Compounds Containing Nitrogen
[1] 24.2.1.3

Write the structures of main products when aniline reacts with the following reagents :

(CH3CO)2O/pyridine

Concept: Amines - Chemical Reactions of Amines - Electrophilic Substitution
Chapter: [0.13] Organic Compounds Containing Nitrogen
[1] 24.2.2

Arrange the following: C2H5NH2, C2H5OH, (CH3)3N – in the increasing order of their boiling point

Concept: Physical Properties of Amines
Chapter: [0.13] Organic Compounds Containing Nitrogen
[1] 24.2.3

Give a simple chemical test to distinguish between the following pair of compounds :

(CH3)2NH and (CH3)3N

Concept: Amines - Chemical Reactions of Amines - Reaction with Arylsulphonyl Chloride
Chapter: [0.13] Organic Compounds Containing Nitrogen
[5] 25 | Attempt any ONE
[5] 25.1

For the hydrolysis of methyl acetate in aqueous solution, the following results were obtained :

 t/s 0 30 60 [CH3COOCH3] / mol L–1 0.6 0.3 0.15

(i) Show that it follows pseudo first order reaction, as the concentration of water remains constant.

(ii) Calculate the average rate of reaction between the time interval 30 to 60 seconds.

(Given log 2 = 0.3010, log 4 = 0.6021)

Concept: Factors Influencing Rate of a Reaction
Chapter: [0.04] Chemical Kinetics
[5] 25.2
[2] 25.2.1
[1] 25.2.1.1

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?

Concept: Factors Influencing Rate of a Reaction
Chapter: [0.04] Chemical Kinetics
[1] 25.2.1.2

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?

Concept: Factors Influencing Rate of a Reaction
Chapter: [0.04] Chemical Kinetics
[3] 25.2.2

A first order reaction takes 30 minutes for 50% completion. Calculate the time required for 90% completion of this reaction.

(log 2 = 0.3010)

Concept: Integrated Rate Equations - Half-life of a Reaction
Chapter: [0.04] Chemical Kinetics
[5] 26 | Attempt any ONE
[5] 26.1
[3] 26.1.1
[1] 26.1.1.1

Account for the following :

Acidic character increases from HF to HI.

Concept: P - Block Group 17 Elements - Concept of Group 17 Elements
Chapter: [0.07] P - Block Elements
[1] 26.1.1.2

Account for the following : There is large difference between the melting and boiling points of oxygen and sulphur.

Concept: Concept of Group 16 Elements
Chapter: [0.07] P - Block Elements
[1] 26.1.1.3

Account for the following : Nitrogen does not form pentahalide.

Concept: P - Block Group 15 Elements - Dinitrogen
Chapter: [0.07] P - Block Elements
[2] 26.1.2
[1] 26.1.2.1

Draw the structures of the following : ClF3

Concept: P - Block Group 17 Elements - Interhalogen Compounds
Chapter: [0.07] P - Block Elements
[1] 26.1.2.2

Draw the structures of the following molecules: XeF4

Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
Chapter: [0.07] P - Block Elements
[5] 26.2
[1] 26.2.1

Which allotrope of phosphorus is more reactive and why?

Concept: P - Block Group 15 Elements - Phosphorus - Allotropic Forms
Chapter: [0.07] P - Block Elements
[1] 26.2.2

How the supersonic jet aeroplanes are responsible for the depletion of ozone layers?

Concept: P - Block Group 16 Elements - Ozone
Chapter: [0.07] P - Block Elements
[1] 26.2.3

F2 has lower bond dissociation enthalpy than Cl2. Why?

Concept: P - Block Group 17 Elements - Concept of Group 17 Elements
Chapter: [0.07] P - Block Elements
[1] 26.2.4

Which noble gas is used in filling balloons for meteorological observations?

Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
Chapter: [0.07] P - Block Elements
[1] 26.2.5

Complete the equation :​ XeF2+PF5

Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
Chapter: [0.07] P - Block Elements

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