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

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Chemistry [Foreign Set 2]
Marks: 70Academic Year: 2014-2015
Date: March 2015

[1]1

What is the formula of a compound in which the element Y forms hcp lattice and atoms of X occupy 2/3rd of tetrahedral voids?

Concept: Close Packed Structures - Formula of a Compound and Number of Voids Filled
Chapter: [1] Solid State
[1]2

Write the IUPAC name of the given compound :

Concept: Amines - Nomenclature
Chapter: [13] Organic Compounds Containing Nitrogen
[1]3

Physisorption is reversible while chemisorption is irreversible. Why ?

Concept: Types of Adsorption
Chapter: [5] Surface Chemistry
[1]4

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

CH3 – CH2 ​– Br and CH3 ​– CH2 ​– I

Concept: Chemical Reactions of Haloalkanes and Haloarenes - Reactions of Haloalkanes - Nucleophilic Substitution Reactions
Chapter: [10] Haloalkanes and Haloarenes
[1]5

Which allotrope of sulphur is thermally stable at room temperature ?

Concept: P - Block Group 15 Elements - Phosphorus - Allotropic Forms
Chapter: [7] P - Block Elements
[2]6
[1]6.1

Following reactions occur at cathode during the electrolysis of aqueous copper(II) chloride solution :

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

Concept: Electrolytic Cells and Electrolysis - Introduction
Chapter: [3] Electrochemistry
[1]6.2

State Kohlrausch law of independent migration of ions.

Concept: Conductance of Electrolytic Solutions - Variation of Conductivity and Molar Conductivity with Concentration
Chapter: [3] Electrochemistry
[2]7

Why do transition elements show variable oxidation states ? In 3d series (Sc to Zn), which elements shows the maximum number of oxidation state and why ?

Concept: General Properties of the Transition Elements (D-block)
Chapter: [8] "D" and "F" Block Elements
[2]8
[1]8.1

Write down the IUPAC name of the following complex :

[Cr(en)3]Cl3

Concept: Nomenclature of Coordination Compounds - Naming of Mononuclear Coordination Compounds
Chapter: [9] Coordination Compounds
[1]8.2

Using IUPAC norms write the formulas for the following: Potassium tetrachloridopalladate(II)

Concept: Nomenclature of Coordination Compounds - Formulas of Mononuclear Coordination Entities
Chapter: [9] Coordination Compounds
[2]9
[1]9.1

Name the reagents used in the following reactions:

Concept: Preparation of Alcohols from Alkenes, Carbonyl Compounds and Grignard Reagents
Chapter: [11] Alcohols, Phenols and Ethers
[1]9.2

Name the reagents used in the following reactions:

Concept: Carboxylic Acids - Methods of Preparation of Carboxylic Acids
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[2]10 | Attempt any one of the following
[1]10.1

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

Concept: Vapour Pressure of Liquid Solutions - Vapour Pressure of Liquid- Liquid Solutions
Chapter: [2] Solutions
[1]10.2

Define azeotropes.

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

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

Concept: Vapour Pressure of Liquid Solutions - Vapour Pressure of Liquid- Liquid Solutions
Chapter: [2] Solutions
[3]11
[1]11.1

Why are alkyl halides insoluble in water?

Concept: Physical Properties of Carboxylic Acids
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]11.2

Why is Butan-1-ol optically inactive but Butan-2-ol is optically active?

Concept: Isomerism in Coordination Compounds - Stereoisomerism
Chapter: [9] Coordination Compounds
[1]11.3

Although chlorine is an electron withdrawing group, yet it is ortho-, para- directing in electrophilic aromatic substitution reactions. Why?

Concept: Introduction to Electrochemistry
Chapter: [3] Electrochemistry
[3]12 | attempt any one of the following
[3]12.1
[1]12.1.1

How will you bring about the following conversions in not more than two steps?

Benzoic acid to Benzaldehyde

Concept: Aldehydes and Ketones - Nomenclature
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]12.1.2

How do you convert the following :

Ethyne to Ethanal

Concept: Carboxylic Acids - Nomenclature
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]12.1.3

How do you convert the following :

Acetic acid to Methane

Concept: Carboxylic Acids - Nomenclature
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[3]12.2
[1]12.2.1

Write the equations involved in the following reactions :

Stephen reaction

Concept: Carboxylic Acids - Nomenclature
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]12.2.2

Write the equations involved in the following reactions :

Wolff-Kishner reduction

Concept: Carboxylic Acids - Nomenclature
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
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[1]12.2.3

Write the equations involved in the following reactions :

Etard reaction

Concept: Carboxylic Acids - Nomenclature
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[3]13

Calculate the mass of NaCl (molar mass = 58.5 g mol−1) to be dissolved in 37.2 g of water to lower the freezing point by 2°C, assuming that NaCl undergoes complete dissociation. (Kf for water = 1.86 K kg mol−1)

Concept: Colligative Properties and Determination of Molar Mass - Osmosis and Osmotic Pressure
Chapter: [2] Solutions
[3]14

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

(i) Terylene
(ii) Bakelite
(iii) Buna-S

Concept: Polymers - Classification of Polymers Based on Structure
Chapter: [15] Polymers
[3]15
[1]15.1

Which one of the following is a monosaccharide:

starch, maltose, fructose, cellulose

Concept: Carbohydrates - Monosaccahrides
Chapter: [14] Biomolecules
[1]15.2

What is the difference between acidic amino acids and basic amino acids?

Concept: Proteins - Amino Acids
Chapter: [14] Biomolecules
[1]15.3

Write the name of the vitamin whose deficiency causes bleeding of gums.

Concept: Introduction of Vitamins
Chapter: [14] Biomolecules
[3]16
[1]16.1

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

Concept: Isomerism in Coordination Compounds - Stereoisomerism
Chapter: [9] Coordination Compounds
[1]16.2

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: [9] Coordination Compounds
[1]16.3

Write the hybridization type and magnetic behaviour of the complex [Ni(CN)4]2−. (Atomic number of Ni = 28)

Concept: Bonding in Coordination Compounds - Magnetic Properties of Coordination Compounds
Chapter: [9] Coordination Compounds
[3]17
[1]17.1

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

Concept: Refining
Chapter: [6] General Principles and Processes of Isolation of Elements
[1]17.2

What is the role of dilute NaCN in the extraction of gold ?

Concept: Concentration of Ores - Leaching
Chapter: [6] General Principles and Processes of Isolation of Elements
[1]17.3

What is 'copper matte' ?

Concept: Occurrence of Metals
Chapter: [6] General Principles and Processes of Isolation of Elements
[3]18

Calculate the emf of the following cell at 25°C :

${E^0}_\left( {Zn}^{2 +} /Zn \right) = - 0 . 76 V, {E^0}_\left( H^+ / H_2 \right) = 0 . 00 V$

Concept: Galvanic Cells - Introduction
Chapter: [3] Electrochemistry
[3]19
[1]19.1

Predict the products of the following reactions :

${CH}_3 - CH = {CH}_2 \to^{i) B_2 H_6}_{ii) 3 H_2 O_2 / {OH}^-} ?$
Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Reduction
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]19.2
$C_6 H_5 - OH \to^{{Br}_2 \left( aq \right)} ?$
Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Oxidation
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[1]19.3

Predict the products of the following reactions :

${CH}_3 {CH}_2 OH \to^{Cu/573 K} ?$
Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Reduction
Chapter: [12] Aldehydes, Ketones and Carboxylic Acids
[3]20

An element X (molar mass = 60 g mol−1) has a density of 6.23 g cm−3. Identify the type of cubic unit cell, if the edge length of the unit cell is 4 ✕ 10−8 cm.

Concept: Oxidation Reduction
Chapter: [6] General Principles and Processes of Isolation of Elements
[3]21
[1]21.1

How would you account the following :

Highest fluoride of Mn is MnF4 whereas the highest oxide is Mn2O7.

Concept: F-block Elements - The Actinoids
Chapter: [8] "D" and "F" Block Elements
[1]21.2

How would you account the following :

Transition metals and their compounds show catalytic properties.

Concept: Chemical Reactions of Haloalkanes and Haloarenes - Reactions of Haloarenes - Reaction with Metals
Chapter: [10] Haloalkanes and Haloarenes
[1]21.3

Complete the following equation :

$3 {MnO}_4^{2 -} + 4 H^+ \to$
Concept: Some Important Compounds of Transition Elements - Oxides and Oxoanions of Metals
Chapter: [8] "D" and "F" Block Elements
[3]22
[1]22.1

Give reasons for the following observations :

A delta is formed at the meeting point of sea water and river water.

Concept: Conductance of Electrolytic Solutions - Introduction
Chapter: [3] Electrochemistry
[1]22.2

Give reasons for the following observations :

NH3 gas adsorbs more readily than N2 gas on the surface of charcoal.

Concept: Adsorption - Mechanism of Adsorption
Chapter: [5] Surface Chemistry
[1]22.3

Give reasons for the following observations :

Powdered substances are more effective  adsorbents.

Concept: Types of Adsorption
Chapter: [5] Surface Chemistry
[4]23

Seeing the growing cases of diabetes and depression among children, Mr. Chopra, the principal of one reputed school organized a seminar in which he invited parents and principals. They all resolved this issue by strictly banning the junk food in schools and by introducing 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. Chopra 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 questions :

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

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

(iii) Why should antidepressant drugs not be taken without consulting a doctor ?

(iv) Give two examples of artificial sweeteners.

Concept: Chemicals in Food - Artificial Sweetening Agents and Food Preservatives
Chapter: [16] Chemistry in Everyday Life
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[5]24 | attempt any one of the following
[5]24.1
[1]24.1.1

Illustrate the following reactions giving suitable example in each case

Ammonolysis

Concept: Physical Properties of Amines
Chapter: [13] Organic Compounds Containing Nitrogen
[1]24.1.2

Illustrate the following reactions giving suitable example in each case

Coupling reaction

Concept: Diazonium Salts - Chemical Reaction of Diazonium Salts - Reactions Involving Retention of Diazo Group Coupling Reactions
Chapter: [13] Organic Compounds Containing Nitrogen
[1]24.1.3

Illustrate the following reactions giving suitable example in each case

Acetylation of amines

Concept: Amines - Chemical Reactions of Amines - Electrophilic Substitution
Chapter: [13] Organic Compounds Containing Nitrogen
[2]24.1.4

Describe Hinsberg method for the identification of primary, secondary and tertiary amines. Also write the chemical equations of the reactions involved.

Concept: Amines - Identification of Primary, Secondary and Tertiary Amines
Chapter: [13] Organic Compounds Containing Nitrogen
[5]24.2
[2]24.2.1

Write the structures of main products when benzene diazonium chloride (C6 H5 N+2CI)C6 H5 N2+CI- reacts with the  :  HBF4/∆

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

Write the structures of main products when benzene diazonium chloride (C6 H5 N+2CI)C6 H5 N2+CI- reacts with the :Cu/HBr

Concept: Preparation of Phenols from Haloarenes, Benzenesulphonic Acid, Diazonium Salts and Cumene
Chapter: [11] Alcohols, Phenols and Ethers
[3]24.2.2

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

$C_6 H_5 {NO}_2 \to^{Sn/HCI} A \to^{{NaNO}_2 /HCI}_{273 K} B \to^{H_2 O}_∆ C$

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

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

${CH}_3 CI \to^{KCN} A \to^{LiAIH} B \to^{{HNO}_2}_{273K} C$
Concept: Preparation of Alcohols from Alkenes, Carbonyl Compounds and Grignard Reagents
Chapter: [11] Alcohols, Phenols and Ethers
[5]25 | attempt any one of the following
[5]25.1
[1]25.1.1

Define activation energy.

Concept: Temperature Dependence of the Rate of a Reaction
Chapter: [4] Chemical Kinetics
[1]25.1.2

Define the following terms: Rate constant

Concept: Chemical Kinetics - Rate Law and Specific Rate Constant
Chapter: [4] Chemical Kinetics
[3]25.1.3

A first order reaction takes 10 minutes for 25% decomposition. Calculate t1/2 for the reaction.

(Given : log 2 = 0.3010, log 3 = 0.4771, log 4 = 0.6021)

Concept: Integrated Rate Equations - Half-life of a Reaction
Chapter: [4] Chemical Kinetics
[5]25.2
[3]25.2.1

For a chemical reaction R → P, the variation in the concentration (R) vs. time (t) plot is given as:

(i) Predict the order of the reaction.

(ii) What is the slope of the curve ?

(iii) Write the unit of rate constant for this reaction.

Concept: Factors Influencing Rate of a Reaction
Chapter: [4] Chemical Kinetics
[2]25.2.2

Show that the time required for 99% completion is double of the time required for the completion of 90% reaction.

Concept: Integrated Rate Equations - Half-life of a Reaction
Chapter: [4] Chemical Kinetics
[5]26 | attempt any one of the following
[5]26.1
[1]26.1.1

Account for the following :

Bond angle in NH+4NH4+ is higher than NH3.

Concept: Bonding in Coordination Compounds - Introduction
Chapter: [9] Coordination Compounds
[1]26.1.2

Account for the following :

H2S has lower boiling point than H2O.

Concept: Colligative Properties and Determination of Molar Mass - Elevation of Boiling Point
Chapter: [2] Solutions
[1]26.1.3

Account for the following :

Reducing character decreases from SO2 to TeO2.

Concept: Oxidation Reduction
Chapter: [6] General Principles and Processes of Isolation of Elements
[1]26.1.4

Draw the structures of the following: H4P2O7 (Pyrophosphoric acid)

Concept: P - Block Group 15 Elements - Oxoacids of Phosphorus
Chapter: [7] P - Block Elements
[1]26.1.5

Draw the structures of the following molecules: XeF2

Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
Chapter: [7] P - Block Elements
[5]26.2
[1]26.2.1

Draw the structures of the following molecules: XeF4

Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
Chapter: [7] P - Block Elements
[1]26.2.2

Draw the structures of the following :

H2S2O7

Concept: P - Block Group 16 Elements - Compounds of Sulphur
Chapter: [7] P - Block Elements
[1]26.2.3

Account for the following :

Iron on reaction with HCl forms FeCl2 nd not FeCl3.

Concept: Uses of Aluminium, Copper, Zinc and Iron
Chapter: [6] General Principles and Processes of Isolation of Elements
[1]26.2.4

Account for the following :

HClO4 is a stronger acid than HClO.

Concept: P - Block Group 17 Elements - Oxoacids of Halogens
Chapter: [7] P - Block Elements
[1]26.2.5

Account for the following :

BiH3 is the strongest reducing agent amongst all the hydrides of group 15.

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