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# Question Paper Solutions - Chemistry 2016 - 2017-CBSE 12th-Class 12 CBSE (Central Board of Secondary Education)

SubjectChemistry
Year2016 - 2017 (March)

#### Alternate Sets

Marks: 70
[1]1

Out of  which is an example of a benzylic halide?

Chapter: [10.01] Haloalkanes
Concept: Haloalkanes and Haloarenes - Nomenclature
[1]2

What is the effect of adding a catalyst on Activation energy (Ea)

Chapter: [4] Chemical Kinetics
Concept: Temperature Dependence of the Rate of a Reaction

What is the effect of catalyst on: Gibbs energy (∆G)

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

Write the formula of the compound of iodine which is obtained when conc. HNO3 oxidises I2

Chapter: [7] P - Block Elements
Concept: P - Block Group 16 Elements - Classification of Oxides
[1]4

What type of colloid is formed when a gas is dispersed in a liquid? Give an example

Chapter: [5] Surface Chemistry
Concept: Classification of Colloids - Classification Based on Type of Particles of the Dispersed Phase, Multimolecular, Macromolecular and Associated Colloids
[1]5

Write the IUPAC name of the following compound:

Chapter: [12.01] Classification, general formulae, structure and nomenclature
Concept: Alcohols, Phenols and Ethers - Nomenclature
[2]6

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

Draw the structures of the following: BrF5

Chapter: [8] Chemistry of p-Block Elements: Group 16, 17, 18
Concept: P - Block Group 17 Elements - Interhalogen Compounds
[2]7

Write the name of the cell which is generally used in transistors. Write the reactions taking place at the anode and the cathode of this cell.

Chapter: [3] Electrochemistry
Concept: Electrolytic Cells and Electrolysis - Introduction
[2]8 | Attempt Any One
[2]8.1

Arrange the following compounds in the increasing order of their acid strength:

p-cresol, p-nitrophenol, phenol

Chapter: [11] Alcohols, Phenols and Ethers
Concept: Physical and Chemical Properties of Alcohols and Phenols

Write the mechanism (using curved arrow notation) of the following reaction:

Chapter: [10.01] Haloalkanes
Concept: Haloalkanes and Haloarenes - Nomenclature
[2]8.2

Write the structures of the products when Butan-2-ol reacts with CrO3

Chapter: [12.01] Classification, general formulae, structure and nomenclature
Concept: Alcohols, Phenols and Ethers - Nomenclature

Write the structures of the products when Butan-2-ol reacts with SOCl2

Chapter: [12.01] Classification, general formulae, structure and nomenclature
Concept: Alcohols, Phenols and Ethers - Nomenclature
[2]9

Using IUPAC norms write the formulae for Potassium trioxalatoaluminate(III)

Chapter: [7] Coordination Compounds
Concept: Importance and Applications of Coordination Compounds

Using IUPAC norms write the formulae for Dichloridobis(ethane-1,2-diamine)cobalt(III)

Chapter: [7] Coordination Compounds
Concept: Importance and Applications of Coordination Compounds
[2]10

Calculate the number of unit cells in 8.1 g of aluminium if it crystallizes in a f.c.c. structure. (Atomic mass of Al = 27 g mol–1)

Chapter: [1] Solid State
Concept: Number of Atoms in a Unit Cell
[3]11

What type of isomerism is shown by the complex [Co(NH3)5(SCN)]2+?

Chapter: [9] Coordination Compounds
Concept: Isomerism in Coordination Compounds - Structural Isomerism

Why is [NiCl4]2− paramagnetic while [Ni(CN)4]2− is diamagnetic? (Atomic number of Ni = 28)

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

Why are low spin tetrahedral complexes rarely observed?

Chapter: [9] Coordination Compounds
Concept: Bonding in Coordination Compounds - Crystal Field Theory (CFT)
[3]12 | Attempt Any One
[3]12.1

Write one difference in Multimolecular colloid and Associated colloid

Chapter: [5] Surface Chemistry
Concept: Colloids - Introduction

Write one difference in Coagulation and Peptization

Chapter: [2] Solutions and Colligative Properties
Concept: Colligative Properties and Determination of Molar Mass - Introduction

Write one difference in Homogeneous catalysis and Heterogeneous catalysis

Chapter: [5] Surface Chemistry
Concept: Catalysis - Homogeneous and Heterogeneous Catalysis
[3]12.2

What are the dispersed phase and dispersion medium in milk?

Chapter: [5] Surface Chemistry
Concept: Emulsions

Write one similarity between Physisorption and Chemisorption

Chapter: [5] Surface Chemistry

Write the chemical method by which Fe(OH)3 sol is prepared from FeCl3.

Chapter: [5] Surface Chemistry
Concept: Preparation of Colloids
[3]13

The cell in which the following reaction occurs:

2Fe^(3+) (aq) + 2I^(-) (aq) ---> 2Fe^(2+) (aq) + I_2 (s) has E_"cell"^@ = 0.236 V at  298 K. Calculate the standard Gibbs energy of the cell reaction. (Given : 1 F = 96,500 C mol−1)

Chapter: [3] Electrochemistry
Concept: Nernst Equation - Electrochemical Cell and Gibbs Energy of the Reaction

How many electrons flow through a metllic wire if a current of 0·5 A is passed for 2 hours? (Given : 1 F = 96,500 C mol−1)

Chapter: [3] Electrochemistry
Concept: Electrochemical Cells
[3]14

Based on the nature of intermolecular forces, classify the following solids:

Sodium sulphate, Hydrogen

Chapter: [1] Solid State
Concept: General Characteristics of Solid State

What happens when CdCl2 is doped with AgCl?

Chapter: [1] Solid State
Concept: Imperfections in Solids - Types of Point Defects - Impurity Defects

Give reasons:Ferrimagnetic substances show better magnetism than antiferromagnetic substances.

Chapter: [2] States of Matters: Structure and Properties Solid State
Concept: Magnetic Properties
[3]15

Explain the principle of the method of electrolytic refining of metals. Give one example.

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

Why does copper obtained in the extraction from copper pyrites have a blistered appearance?

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

What is the role of depressants in the froth floatation process?

Chapter: [6] General Principles and Processes of Isolation of Elements
Concept: Concentration of Ores - Froth Floatation Method
[3]16

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

Chapter: [9] Coordination Compounds
Concept: Definitions of Some Important Terms Pertaining to Coordination Compounds

Write the structures of compounds A, B and C in the following reactions

Chapter: [9] Coordination Compounds
Concept: Definitions of Some Important Terms Pertaining to Coordination Compounds
[3]17

Give reasons  Acetylation of aniline reduces its activation effect.

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

Give reasons for the following:

CH3NH2 is more basis than C6H5NH2.

Chapter: [13] Organic Compounds Containing Nitrogen
Concept: Classification of Amines

Give reasons  Although –NH2 is o/p directing group, yet aniline on nitration gives a significant amount of m-nitroaniline

Chapter: [15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt
Concept: Amines - Nomenclature
[3]18

Give reasons for the following:

Red phosphorus is less reactive than white phosphorus.

Chapter: [7.01] Group 15 Elements
Concept: P - Block Group 15 Elements - Phosphorus - Allotropic Forms

Give reasons for the following:

Electron gain enthalpies of halogens are largely negative.

Chapter: [7] P - Block Elements
Concept: Compounds of Halogens

Give reasons for the following: N2O5 is more acidic than N2O3

Chapter: [7] P - Block Elements
Concept: P - Block Group 16 Elements - Classification of Oxides
[3]19

Explain the following terms with suitable examples Cationic detergents

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

What is meant by the term ‘broad spectrum antibiotics’? Explain.

Chapter: [16] Chemistry in Everyday Life
Concept: Therapeutic Action of Different Classes of Drugs - Antimicrobials

Explain Tranquilizers

Chapter: [16.01] Chemicals in Medicines
Concept: Drugs and Their Classification
[3]20

Write the names of monomers used for getting the following polymers:

Teflon

Chapter: [15] Polymers
Concept: Polymers - Classification of Polymers Based on Structure

Write the structures of the monomers used for getting the following polymers

Melamine – formaldehyde polymer

Chapter: [15] Polymers
Concept: Polymers - Some Important Polymers

Write the name of monomers used for getting the following polymers : Neoprene

Chapter: [15] Polymers
Concept: Polymers - Classification of Polymers Based on Molecular Forces
[3]21

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.

Chapter: [9] Coordination Compounds
Concept: Definitions of Some Important Terms Pertaining to Coordination Compounds
[4]22

A first order reaction takes 20 minutes for 25% decomposition. Calculate the time when 75% of the reaction will be completed.

(Given : log = 2 = 0·3010, log 3 = 0·4771, log 4 = 0·6021)

Chapter: [4] Chemical Kinetics
Concept: Integrated Rate Equations - First Order Reactions
[4]23

After watching a programme on TV about the presence of carcinogens (cancer causing agents) Potassium bromate and Potassium iodate in bread and other bakery products, Ritu a class XII student decided to aware others about the adverse effects of these carcinogens in foods. She consultanted the school principal and requested him to instruct canteen contractor to stop selling sandwiches, pizza, burgers and other bakery products to the students. Principal took an immediate action and instructed the canteen contractor to replace the bakery products with some proteins and vitamins rich food like fruits, salads, sprouts etc. The decision was welcomed by the parents and students.

1) What are the values (at least two) displayed by Ritu?

2) Which polysaccharide component of carbohydrates is commonly present in bread?

3) Write the two types of secondary structure of proteins.

4) Give two examples of water soluble vitamins.

Chapter: [17] Biomolecules – carbohydrates, proteins, enzymes, vitamins and nucleic acids
Concept: Introduction of Proteins
[5]24 | Attempt Any One
[5]24.1

Write the product(s) in the following reactions:

Chapter: [10.01] Haloalkanes
Concept: Haloalkanes and Haloarenes - Nomenclature

Write the product(s) in the following reactions:

Chapter: [10.01] Haloalkanes
Concept: Haloalkanes and Haloarenes - Nomenclature

Write the product(s) in the following reactions:

Chapter: [10.01] Haloalkanes
Concept: Haloalkanes and Haloarenes - Nomenclature

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

Butanal and Butan-2-one

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

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

Chapter: [12.05] Distinction between primary, secondary and tertiary alcohols
Concept: Chemical Reactions of Phenols (Only)
[5]24.2

Write the equations involved in the following reactions:

Etard reaction

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

Write the reaction involved in the Stephen reduction

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

How will you convert the following in not more than two steps:

Benzoic acid to Benzaldehyde

Chapter: [2] Solutions
Concept: Abnormal Molar Masses

How will you convert the following in not more than two steps:

Acetophenone to Benzoic acid

Chapter: [2] Solutions
Concept: Abnormal Molar Masses

How will you convert the following in not more than two steps:

Ethanoic acid to 2-Hydroxyethanoic acid

Chapter: [2] Solutions and Colligative Properties
Concept: Types of Solutions
[5]25 | Attempt Any One
[5]25.1

Give reasons: Transition metals show variable oxidation states.

Chapter: [10] Chemistry of Transition and Inner-Transition Elements: d-Block: 3d, 4d and 5d series f-Block: 4f and 5f series
Concept: General Properties of the Transition Elements (D-block)

Account for the following:

Zn, Cd and Hg are soft metals.

Chapter: [8.02] F-block Elements
Concept: F-block Elements - The Lanthanoids

Account for the following:

E° value for the Mn3+/Mn2+ couple is highly positive (+1.57 V) as compare to Cr3+/Cr2+.

Chapter: [3] Electrochemistry
Concept: Galvanic Cells - Measurement of Electrode Potential

Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.

Chapter: [8] "D" and "F" Block Elements
Concept: F-block Elements - The Actinoids
[5]25.2

Following are the transition metal ions of 3d series:

Ti4+, V2+, Mn3+, Cr3+

(Atomic numbers: Ti = 22, V = 23, Mn = 25, Cr = 24)

1) Which ion is most stable in an aqueous solution and why?

2) Which ion is a strong oxidising agent and why?

3) Which ion is colourless and why?

Chapter: [10] Chemistry of Transition and Inner-Transition Elements: d-Block: 3d, 4d and 5d series f-Block: 4f and 5f series
Concept: General Properties of the Transition Elements (D-block)

Complete the following equations:

2MnO_4^(-)+16H^++5S^(2-)rarr

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

Complete the following equations:

KMnO4

Chapter: [7.03] Group 17 Elements
Concept: P - Block Group 17 Elements - Concept of Group 17 Elements
[5]26 | Attempt Any One
[5]26.1

A 10% solution (by mass) of sucrose in water has freezing point of 269.15 K. Calculate the freezing point of 10% glucose in water, if freezing point of pure water is 273.15 K

Given : (Molar mass of sucrose = 342 g mol−1)

(Molar mass of glucose = 180 g mol−1)

Chapter: [14] Biomolecules
Concept: Carbohydrates - Preparation of Glucose from Sucrose (Cane Sugar) and Starch

Define Molality

Chapter: [2] Solutions and Colligative Properties
Concept: Expressing Concentration of Solutions

Define the term Abnormal molar mass

Chapter: [2] Solutions
Concept: Abnormal Molar Masses
[5]26.2

30 g of urea (M = 60 g mol−1) is dissolved in 846 g of water. Calculate the vapour pressure of water for this solution if vapour pressure of pure water at 298 K is 23·8 mm Hg.

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

Write two differences between an ideal solution and a non-ideal solution.

Chapter: [2] Solutions and Colligative Properties
Concept: Types of Solutions
S