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Question Paper Solutions - Chemistry 2014 - 2015-CBSE 12th-Class 12 CBSE (Central Board of Secondary Education)

Alternate Sets

     

Marks: 70
[1]1

What is the basicity of H3PO4 ?

Chapter: [7.01] Group 15 Elements
Concept: P - Block Group 15 Elements - Compounds of Phosphorus
[1]2

Write the IUPAC name of the given compound :

Chapter: [9] Coordination Compounds
Concept: Nomenclature of Coordination Compounds - Naming of Mononuclear Coordination Compounds
[1]3

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

Chapter: [10.01] Haloalkanes
Concept: Chemical Reactions of Haloalkanes and Haloarenes - Reactions of Haloalkanes - Nucleophilic Substitution Reactions
[1]4

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

Chapter: [5] Surface Chemistry
Concept: Properties of Colloidal Solutions
[1]5

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?

Chapter: [1] Solid State
Concept: Crystal Lattices and Unit Cells - Introduction
[2]6

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

Chapter: [8] "D" and "F" Block Elements
Concept: General Properties of the Transition Elements (D-block)
[2]7
[1]7.1

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

Chapter: [9] Coordination Compounds
Concept: Nomenclature of Coordination Compounds - Naming of Mononuclear Coordination Compounds
[1]7.2

Write the formula for the following complex:

Pentaamminenitrito-o-Cobalt (III).

Chapter: [9] Coordination Compounds
Concept: Nomenclature of Coordination Compounds - Formulas of Mononuclear Coordination Entities
[2]8
[1]8.1

Name the reagents used in the following reactions:

Chapter: [11] Alcohols, Phenols and Ethers
Concept: Preparation of Alcohols from Alkenes, Carbonyl Compounds and Grignard Reagents
[1]8.2

Name the reagents used in the following reactions:

Chapter: [14.01] Carboxylic acids
Concept: Carboxylic Acids - Methods of Preparation of Carboxylic Acids
[2]9
[1]9.1

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

Chapter: [2] Solutions
Concept: Vapour Pressure of Liquid Solutions - Vapour Pressure of Liquid- Liquid Solutions
[1]9.2

Define azeotropes. 

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

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

Chapter: [2] Solutions
Concept: Vapour Pressure of Liquid Solutions - Vapour Pressure of Liquid- Liquid Solutions
[2]10
[1]10.1

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 ?

Chapter: [3] Electrochemistry
Concept: Relation Between Gibbs Energy Change and Emf of a Cell
[1]10.2

Define limiting molar conductivity.

Chapter: [6.04] Electrolytic conductance
Concept: Conductance of Electrolytic Solutions - Variation of Conductivity and Molar Conductivity with Concentration

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

Chapter: [6.04] Electrolytic conductance
Concept: Conductance of Electrolytic Solutions - Variation of Conductivity and Molar Conductivity with Concentration
[3]11

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)

Chapter: [2] Solutions and Colligative Properties
Concept: Abnormal Molar Masses
[3]12
[1]12.1

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

Chapter: [10] Chemistry of Transition and Inner-Transition Elements: d-Block: 3d, 4d and 5d series f-Block: 4f and 5f series
Concept: Occurrence of Metals
[1]12.2

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

Chapter: [10] Chemistry of Transition and Inner-Transition Elements: d-Block: 3d, 4d and 5d series f-Block: 4f and 5f series
Concept: Occurrence of Metals
[1]12.3

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

Chapter: [10] Chemistry of Transition and Inner-Transition Elements: d-Block: 3d, 4d and 5d series f-Block: 4f and 5f series
Concept: Occurrence of Metals
[3]13

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?

Chapter: [1] Solid State
Concept: Number of Atoms in a Unit Cell
[3]14
[2]14.1
[1]14.1.1

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

Chapter: [8.02] F-block Elements
Concept: F-block Elements - The Actinoids
[1]14.1.2

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

Chapter: [8] "D" and "F" Block Elements
Concept: General Properties of the Transition Elements (D-block)
[1]14.2

Complete the following equation :

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

 

Chapter: [8] "D" and "F" Block Elements
Concept: Some Important Compounds of Transition Elements - Oxides and Oxoanions of Metals
[3]15
[1]15.1

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

Chapter: [7] Coordination Compounds
Concept: Isomerism in Coordination Compounds - Stereoisomerism
[1]15.2

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

Chapter: [7] Coordination Compounds
Concept: Bonding in Coordination Compounds - Crystal Field Theory (CFT)
[1]15.3

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

(At.no. of Ni = 28)

Chapter: [9] Coordination Compounds
Concept: Bonding in Coordination Compounds - Magnetic Properties of Coordination Compounds
[3]16

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

Chapter: [4] Electrochemistry
Concept: Galvanic Cells - Introduction
[3]17
[1]17.1

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

Chapter: [5] Surface Chemistry
Concept: Properties of Colloidal Solutions
[1]17.2

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

Chapter: [5] Surface Chemistry
Concept: Classification of Colloids - Classification Based on Nature of Interaction Between Dispersed Phase and Dispersion Medium
[1]17.3

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

Chapter: [5] Surface Chemistry
Concept: Catalysis - Enzyme Catalysis
[3]18

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

(i) Nylon-6, 6

(ii) PHBV

(iii) Neoprene

Chapter: [15] Polymers
Concept: Introduction of Polymers
[3]19
[1]19.1

Predict the products of the following reactions :

Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Reduction
[1]19.2

Predict the products of the following reactions :

Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Oxidation
[1]19.3

Predict the products of the following reactions :

Chapter: [12.02] Carboxylic Acids
Concept: Carboxylic Acids - Chemical Reactions of Carboxylic Acids - Reactions Involving –COOH Group
[3]20 | Attempt any ONE
[3]20.1
[1]20.1.1

How do you convert the following : Phenol to anisole

Chapter: [11] Alcohols, Phenols and Ethers
Concept: Preparation of Ethers from Dehydration of Alcohols and Williamson Systhesis
[1]20.1.2

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

Chapter: [11] Alcohols, Phenols and Ethers
Concept: Preparation of Alcohols from Alkenes, Carbonyl Compounds and Grignard Reagents
[1]20.1.3

How do you convert the following : Aniline to phenol

Chapter: [11] Alcohols, Phenols and Ethers
Concept: Preparation of Phenols from Haloarenes, Benzenesulphonic Acid, Diazonium Salts and Cumene
[3]20.2

Write the mechanism of the following reaction :

Chapter: [11] Alcohols, Phenols and Ethers
Concept: Chemical Reactions of Alcohols and Phenols - Reactions Involving Cleavage of Carbon–Oxygen (C–O) Bond in Alcohols

Write the equation involved in the acetylation of Salicylic acid.

Chapter: [11] Alcohols, Phenols and Ethers
Concept: Chemical Reactions of Alcohols and Phenols - Reactions Involving Cleavage of O–H Bond
[3]21
[1]21.1

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

Chapter: [14] Biomolecules
Concept: Carbohydrates - Oligosaccharides
[1]21.2

What is the difference between fibrous protein and globular protein ?

Chapter: [17] Biomolecules – carbohydrates, proteins, enzymes, vitamins and nucleic acids
Concept: Introduction of Proteins
[1]21.3

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

Chapter: [14.03] Vitamins
Concept: Introduction of Vitamins
[3]22
[1]22.1

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

Chapter: [10.01] Haloalkanes
Concept: Physical Properties of Haloalkanes and Haloarenes
[1]22.2

Give reasons : Racemic mixture is optically inactive.

Chapter: [10] Haloalkanes and Haloarenes
Concept: Haloalkanes - R-s and D-l Configuration
[1]22.3

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

Chapter: [10.02] Haloarenes
Concept: Chemical Reactions of Haloalkanes and Haloarenes - Reactions of Haloarenes - Nucleophilic Substitution
[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.

After reading the above passage, answer the following :

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

(ii) As a student, how can you spread awareness about this issue ?

(iii) What are tranquillizers ? Give an example.

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

Chapter: [16.02] Chemicals in Food
Concept: Chemicals in Food - Artificial Sweetening Agents and Food Preservatives
[5]24 | Attempt any ONE
[5]24.1
[3]24.1.1
[1]24.1.1.1

Account for the following :

Acidic character increases from HF to HI.

Chapter: [7.03] Group 17 Elements
Concept: P - Block Group 17 Elements - Concept of Group 17 Elements
[1]24.1.1.2

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

Chapter: [8] Chemistry of p-Block Elements: Group 16, 17, 18
Concept: Concept of Group 16 Elements
[1]24.1.1.3

Account for the following : Nitrogen does not form pentahalide.

Chapter: [7.01] Group 15 Elements
Concept: P - Block Group 15 Elements - Dinitrogen
[2]24.1.2
[1]24.1.2.1

Draw the structures of the following : ClF3

Chapter: [8] Chemistry of p-Block Elements: Group 16, 17, 18
Concept: P - Block Group 17 Elements - Interhalogen Compounds
[1]24.1.2.2

Draw the structures of the following molecules: XeF4

Chapter: [8] Chemistry of p-Block Elements: Group 16, 17, 18
Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
[5]24.2
[1]24.2.1

Which allotrope of phosphorus is more reactive and why?

Chapter: [7] P - Block Elements
Concept: P - Block Group 15 Elements - Phosphorus - Allotropic Forms
[1]24.2.2

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

Chapter: [9] Preparation/ Manufacture, Properties and Uses of Compounds of Groups 16, 17, – Ozone, Sulphur Dioxide, Sulphuric Acid, Hydrochloric Acid
Concept: P - Block Group 16 Elements - Ozone
[1]24.2.3

F2 has lower bond dissociation enthalpy than Cl2. Why?

Chapter: [7.03] Group 17 Elements
Concept: P - Block Group 17 Elements - Concept of Group 17 Elements
[1]24.2.4

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

Chapter: [8] Chemistry of p-Block Elements: Group 16, 17, 18
Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
[1]24.2.5

Complete the equation :​ XeF2+PF5 

Chapter: [8] Chemistry of p-Block Elements: Group 16, 17, 18
Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
[5]25 | Attempt any ONE
[5]25.1

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 :

Chapter: [15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt
Concept: Amines - Preparation of Amines
[5]25.2
[3]25.2.1
[1]25.2.1.1

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

Br2 water

Chapter: [15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt
Concept: Amines - Chemical Reactions of Amines - Electrophilic Substitution
[1]25.2.1.2

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

Chapter: [15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt
Concept: Amines - Chemical Reactions of Amines - Basic Character of Amines
[1]25.2.1.3

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

(CH3CO)2O/pyridine

Chapter: [15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt
Concept: Amines - Chemical Reactions of Amines - Electrophilic Substitution
[1]25.2.2

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

Chapter: [13.01] Amines
Concept: Physical Properties of Amines
[1]25.2.3

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

(CH3)2NH and (CH3)3N

Chapter: [13.01] Amines
Concept: Amines - Chemical Reactions of Amines - Reaction with Arylsulphonyl Chloride
[5]26 | Attempt any ONE
[5]26.1

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

t/s 0 30 60
[CH3COOCH3] / mol L–1 0.60 0.30 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)

Chapter: [5] Chemical Kinetics
Concept: Factors Influencing Rate of a Reaction
[5]26.2
[2]26.2.1

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?

Chapter: [5] Chemical Kinetics
Concept: Factors Influencing Rate of a Reaction

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?

Chapter: [5] Chemical Kinetics
Concept: Factors Influencing Rate of a Reaction
[3]26.2.2

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

(log 2 = 0.3010)

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