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Chemistry (Theory) 2012-2013 ISC (Arts) Class 12 Question Paper Solution

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Chemistry (Theory)
Marks: 70Academic Year: 2012-2013
Date: March 2013

Answer all questions in Part I and six questions from Part II, choosing two questions from Section A, two from Section B and two from Section C.


PART I
[20]1
[5]1.a

Fill in the blanks by choosing the appropriate word/words from those given in the brackets :

(zero, first, second, increased, decreased, anode, cathode, active, inactive, potassium cyanide, internal, external, dependent, independent, red, benzoic acid, benzoin, common ion effect, salt hydrolysis, alkali, potassium hydroxide,)

(i) In a galvanic cell, electrons flow from ………. to ……….. through the connecting wires.

(ii) Racemic mixtures are optical …………. because of …………… compensation.

(iii) The half-life period of a …………. order reaction is …………. of the concentration of the reactant.

(iv) Benzaldehyde when treated with an alcoholic solution of ……… forms ………..

(v) The solubility of calcium oxalate is …………. in the presence of ammonium oxalate because of ……… .

Concept: Galvanic Cells, Mechanism of Current Production in a Galvanic Cell; - Electrochemical Series
Chapter: [6.02] Galvanic cells, mechanism of current production in a galvanic cell;
[5]1.b | Complete the following statements by selecting the correct alternative from the choices given:
[1]1.b.i

The compound which is optically active is:

1-butanol

2-butanol

1-propanol

2-methyl-1-propanol

Concept: Aniline - Importance in Synthesis of Other Organic Compounds
Chapter: [0.15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt
[1]1.b.ii

The salt which will not hydrolyse in aqueous solution is: 

Copper sulphate

Sodium sulphate

Potassium cyanide

Sodium carbonate

Concept: Ionic Equilibria - Salt Hydrolysis
Chapter: [5.03] Salt hydrolysis
[1]1.b.iii

Copper has the face centred cubic structure. The coordination number of each ion is:

4

12

14

8

Concept: Occurrence of Metals
Chapter: [0.1] Chemistry of Transition and Inner-Transition Elements: d-Block: 3d, 4d and 5d series f-Block: 4f and 5f series
[1]1.b.iv

For the reaction 2SO2 + O2 ⇌ 2SO3, the unit of an equilibrium constant is :

L mol-1

J mol-1

mol L-1

[L mol-1]2

Concept: Reversible Reactions and Dynamic Equilibrium - Simple Calculations of Equilibrium Constant and Concentration
Chapter: [4.01] Reversible reactions and dynamic equilibrium
[1]1.b.v

The deficiency of vitamin D causes:

Rickets

Gout

Scurvy

Night blindness.

Concept: Vitamins - Vitamin Deficiency Diseases
Chapter: [0.17] Biomolecules – carbohydrates, proteins, enzymes, vitamins and nucleic acids
[5]1.c | Answer the following questions:
[1]1.c.i

Two metallic elements A and B have the following standard oxidation potentials: A = 0·40v B = - 0·80v. What would you expect if element A was added to an aqueous salt solution of element B? Give a reason for your answer.

Concept: General Properties of the Transition Elements (D-block)
Chapter: [0.1] Chemistry of Transition and Inner-Transition Elements: d-Block: 3d, 4d and 5d series f-Block: 4f and 5f series
[1]1.c.ii

Two moles of NH3 are introduced into the one-litre flask in which it dissociates at high temperature as follows: 2NH3(g)  ⇌ N2(g) + 3H2(g). Determine Kc, if at equilibrium 1 mole of NH3 remains.

Concept: Order of a Reaction - Characteristics of First Order Reaction
Chapter: [3.01] Order of a reaction
[1]1.c.iii

Give a balanced equation for the preparation of salicylaldehyde from phenol.

Concept: Alcohols - Methods of Preparation
Chapter: [12.01] Methods of preparation, manufacture, properties and use
[1]1.c.iv

If the half-life period for a first-order reaction is 69-3 seconds, what is the value of its rate constant?

Concept: Order of a Reaction - Derivation of Expression of Half-life Period from First Order Rate Equation
Chapter: [3.01] Order of a reaction
[1]1.c.v

Define cryoscopic constant. 

Concept: Relative Molecular Mass of Non-volatile Substances - Freezing Point Depression
Chapter: [1.03] Relative molecular mass of non-volatile substances
[5]1.d

Match the following:

(i) Colligative property (a) Polysaccharide
(ii) Nicol prism (b) Osmotic pressure
(iii) Activation energy (c) Aldol condensation
(iv) Starch (d) Polarimeter
(v) Acetaldehyde (e) Arrhenius equation
Concept: Vapour Pressure of Liquid Solutions - Vapour Pressure of Liquid- Liquid Solutions
Chapter: [1.01] Raoult's law and colligative properties
PART II (50 Marks)
[10]2
SECTION - A (20 marks ) Answer any two questions.
[5]2.a
[3]2.a.i

Ethylene glycol is used as an antifreeze agent. Calculate the amount of ethylene glycol to be added to 4 kg of water to prevent it from freezing at -6°C. (Kf for H2O = 1 .85 K mole-1 kg)

Concept: Relative Molecular Mass of Non-volatile Substances - Depression in Freezing Point
Chapter: [1.03] Relative molecular mass of non-volatile substances
[2]2.a.ii

The freezing point of a solution containing 0·3gms of acetic acid in 30gms of benzene is lowered by 0.45K. Calculate the Van't Hoff factor. (at. wt. of C = 12, H = 1, O = 16, Kf for benzene = 5· 12K kg mole-1). 

Concept: Relative Molecular Mass of Non-volatile Substances - Freezing Point Depression
Chapter: [1.03] Relative molecular mass of non-volatile substances
[2]2.b | Name the Iaw or principle confirmed by the following observations:
[1]2.b.i

When water is added to 0.01M aqueous solution of acetic acid the number of hydrogen ions increases.

Concept: Ionic Equilibria - Ostwald’s Dilution Law and Its Derivation
Chapter: [5.06] Ostwald’s dilution law and its derivation
[1]2.b.ii

When 96500 coulombs of electricity is passed through acidulated water, 5·6 litres of oxygen at s.t.p. is liberated at the anode.

Concept: Faraday’S Laws of Electrolysis, Coulometer - Faraday’S Laws of Electrolysis
Chapter: [6.01] Faraday’s laws of Electrolysis, Coulometer
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[1]2.c

Arrange Ag, Cr and Hg metals in the increasing order of reducing power. Given:

`(E_(Ag^+)^o)/(Ag) = +0.80V`

`(E_(Cr^(+3))^o)/(Cr) = -0.74V`

`(E_(Hg^(+2))^o)/(Hg) = +0.79V`

Concept: Galvanic Cells, Mechanism of Current Production in a Galvanic Cell; - Galvanic Cells - Introduction
Chapter: [6.02] Galvanic cells, mechanism of current production in a galvanic cell;
[2]2.d

In a first-order reaction, 10% of the reactant is consumed in 25 minutes  Calculate: 

(i) The half-life of the reaction.
(ii) The time required for completing 17% of the reaction.

Concept: Order of a Reaction - Definition of Half-life Period
Chapter: [3.01] Order of a reaction
[10]3
[4]3.a | Explain giving reasons why (Give equations in support of your answer):
[2]3.a.i

A solution of NH4Cl and NH4OH acts as a buffer.

Concept: Ionic Equilibria - Buffer Solutions
Chapter: [5.04] Buffer solutions
[2]3.a.ii

Cu is precipitated as CuS while  Zn is not precipitated when H2S is passed through an acidic solution of Cu(NO3 )2  and Zn(NO3)2 respectively.

Concept: Ionic Equilibria - Buffer Solutions
Chapter: [5.04] Buffer solutions
[4]3.b
[1]3.b.i

What is Schottky defect in a solid?

Concept: States of Matters: Structure and Properties Solid State - Point Defects – F Centers
Chapter: [0.02] States of Matters: Structure and Properties Solid State
[2]3.b.ii

A bcc element (atomic mass 65) has a cell edge of 420 pm. Calculate its density in gms/cm3 .

Concept: States of Matters: Structure and Properties Solid State - Calculation of Density of Unit Cell
Chapter: [0.02] States of Matters: Structure and Properties Solid State
[2]3.c

The rate of the reaction`H_2 +I_2 ⇌ 2HI` is  given by:
                       Rate = 1.7 × 10-19 [H2] [I2] at 25°C.
The rate of decomposition of gaseous HI to H2 and I2 is given by:
                      Rate = 2.4 × 10-21 [HI]2 at 25°C.
Calculate the equilibrium constant for the formation of HI from H2 and I2 at 25°C.

Concept: Chemical Equilibria - Reversible Reactions and Dynamic Equilibrium
Chapter: [4.01] Reversible reactions and dynamic equilibrium
[10]4
[2]4.a
[1]4.a.i

Give Lewis's definition of acids and bases.

Concept: Acids, Bases and Salts - Arrhenius, BroNsted-lowry and Lewis Concept of Acids and Bases
Chapter: [5.01] Arrhenius, Brönsted-Lowry and Lewis concept of acids and bases
[1]4.a.ii

 The solubility of Ag2CrO4 at 25°C is 8.0 × 10-5 moles litre-1. Calculate its solubility product.

Concept: Solubility Product and Its Applications - Solubility product
Chapter: [5.05] Solubility product and its applications
[5]4.b
[2]4.b.i

Define the molar conductance of a solution. State its unit. How is it related to the specific conductance of a solution? 

Concept: Electrolytic Conductance - General Relationship Between
Chapter: [6.04] Electrolytic conductance
[3]4.b.ii

Calculate the value of Ecell at 298 K for the following cell:

`(Al)/(Al^(3+)) (0.01M) || Sn^(2+) ((0.015 M))/(Sn)`

`E°  _(Al^(3+))/(AI)= -1.66 " Volt and " E° _(Sn^(2+)) /(Sn) = -0.14` volt

Concept: Nernst Equation - Introduction
Chapter: [6.02] Galvanic cells, mechanism of current production in a galvanic cell;
[3]4.c
[1]4.c.i

Calculate the degree of hydrolysis of 0.2 (M) sodium acetate solution. 
(Hydrolysis constant of sodium acetate = 5.6 × 10-10 and ionic product of H2O = 10-14 at 25°C).

Concept: Ionic Equilibria - Common Ion Effect Example
Chapter: [5.07] Common ion effect
[2]4.c.ii

Explain why high pressure is used in the manufacture of ammonia by Haber's process. Stiite the law or principle used.

Concept: Reversible Reactions and Dynamic Equilibrium - Synthesis of Ammonia by Haber’s Proces
Chapter: [4.01] Reversible reactions and dynamic equilibrium
SECTION-B (10 marks) Answer any two questions.
[5]5
[2]5.a

Give the IUPAC names of the following coordination compounds:
(i) K2[Zn(OH)4]
(ii) [CO(NH3)5 (CO3)] Cl.

Concept: Coordination Compounds - IUPAC rules of nomenclature of coordination compounds
Chapter: [0.07] Coordination Compounds
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[1]5.b

For the complex ion [Fe (CN)6]3- state: 
(i) The geometry of the ion.
(ii) The magnetic property of the ion.

Concept: Potassium Permanganate
Chapter: [0.1] Chemistry of Transition and Inner-Transition Elements: d-Block: 3d, 4d and 5d series f-Block: 4f and 5f series
[2]5.c

What type of structural isomers are [Co(NH3)5 Br] SO4 and [Co(NH3)5 SO4]Br? Give a chemical test to distinguish the isomers. 

Concept: Isomerism in Coordination Compounds - Stereoisomerism
Chapter: [0.07] Coordination Compounds
[5]6
[2]6.a

For the molecule XeF2 :
(i) Draw the structure of the molecule indicating the lone pairs.
(ii) State the hybridization of the central atom.
(iii) State the ge.ometry of the molecule.

Concept: Hybridization, Shape and Structure of Compounds
Chapter: [0.08] Chemistry of p-Block Elements: Group 16, 17, 18
[3]6.b

Give balanced chemical equations for the following reactions: 
(i) Fluorine treated with a dilute sodium hydroxide solution.
(ii) Hydrogen sulphide treated with concentrated sulphuric acid.
(iii) Potassium iodide treated with acidified potassium pennanganate solution. 

Concept: P - Block Group 17 Elements - Reaction of Fluorine
Chapter: [0.08] Chemistry of p-Block Elements: Group 16, 17, 18
[5]7
[2]7.a

In the extraction of zinc from zinc blende:

(i) Give an equation to show how zinc oxide is converted to zinc.
(ii) How is impure zinc finally electro-refined? 

Concept: Occurrence of Metals
Chapter: [0.1] Chemistry of Transition and Inner-Transition Elements: d-Block: 3d, 4d and 5d series f-Block: 4f and 5f series
[3]7.b

Explain why:
(i) Transition elements form coloured compounds. 
(ii) Interhalogen compounds are more reactive than their constituent elements.
(iii) Cu+ is diamagnetic but Cu2+ is paramagnetic. (Z = 29)

Concept: Magnetic Properties
Chapter: [0.02] States of Matters: Structure and Properties Solid State
SECTION-C(20 marks) Answer any two questions.
[10]8
[7]8.a | How can the following conversions be brought about:
[3]8.a.i

Nitrobenzene to benzene diazonium chloride.

Concept: Nitrobenzene Method of Preparation
Chapter: [0.15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt
[2]8.a.ii

Propanoic acid to ethylamine.

Concept: Alcohols, Phenols and Ethers - Nomenclature
Chapter: [12.04] Classification, general formulae, structure and nomenclature [13.02] Ethers
[2]8.a.iii

Benzoic acid to benzaldehyde.  

Concept: Benzoic Acid - Benzoic acid Preparation from benzaldehyde and Toluene
Chapter: [14.01] Carboxylic acids
[3]8.b

Identify the compounds A, B, C, D, E and F:  

Concept: Introduction of Aldehydes, Ketones and Carboxylic Acids
Chapter: [13.01] Carbonyl compounds
[5]9
[1]9.a

Acetamide is heated with bromine and sodium hydroxide solution.

Concept: Acid Derivatives - Acetamide - Acid Hydrolysis
Chapter: [14.02] Acid derivatives

Benzaldehyde is treated with 50% sodium hydroxide solution.

Concept: Aldehydes and Ketones - Benzaldehyde Reactions with Ammonia and Its Derivatives
Chapter: [13.01] Carbonyl compounds
[2]9.b

Give one chemical test to distinguish between the following pair of compounds: Acetone and phenol.

Concept: Phenols - Phenols
Chapter: [12.03] Distinction between primary, secondary and tertiary alcohols

Give one chemical test to distinguish between the following pair of compounds: Formic acid and acetic acid.

Concept: Carboxylic Acids - Tests for Acids: Formic Acid and Acetic Acid
Chapter: [14.01] Carboxylic acids
[2]9.c

Name the type of isomerism exhibited by the following pairs of compound:
(1) (C2H5)2NH and CH3-NH-C3H7
(2) 1 – butanol and 2 methyl-1 -propanol.

Concept: Isomerism in Coordination Compounds - Stereoisomerism
Chapter: [0.07] Coordination Compounds

Name the type of isomerism that the compound with molecular formula C3H6O2 exhibits. Represent the isomers.

Concept: Isomerism in Coordination Compounds - Stereoisomerism
Chapter: [0.07] Coordination Compounds
[10]10
[4]10.a

Write balanced chemical equations for the following reactions:
Oxalic acid is treated with acidified potassium permanganate solution.

Concept: Oxalic Acid - Oxidation by Potassium Permanganate
Chapter: [14.01] Carboxylic acids

Write balanced chemical equation for the following reaction: 
Benzoic acid is treated with a mixture of concentrated nitric acid and concentrated sulphuric acid.

Concept: Benzoic Acid - Benzoic Acid Reaction with Sodium Hydroxide, Sodium Carbonate
Chapter: [14.01] Carboxylic acids

Write balanced chemical equation for the following reaction:
Methyl magnesium iodide is treated with carbon dioxide and the product hydrolysed in acidic medium.

Concept: Acid Derivatives - Acetic Anhydride - Hydrolysis
Chapter: [14.02] Acid derivatives

Write balanced chemical equation for the following reaction:
Ethylacetate is treated with ammonia.

Concept: Acid Derivatives - Ethyl Acetate Reaction with Ammonia
Chapter: [14.02] Acid derivatives
[4]10.b

An organic compound [A] having molecular formula C2H7N on treatment with nitrous acid gives a compound [B] having molecular formula C2H6O. [B] on treatment with an organic compound [C] gives a carboxylic acid [D] and a sweet-smelling compound [E]. Oxidation of [B] with acidified potassium dichromate also gives [D].
(i) Identify [A], [B], [C], [D] and [E].
(ii) Write a balanced chemical equation of [D] with chlorine in the presence of red phosphorus and name the reaction.

Concept: Aniline - Importance in Synthesis of Other Organic Compounds
Chapter: [0.15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt
[2]10.c

Acetamide is amphoteric in nature. Give two equations to support this statement.

Concept: Acid Derivatives - Acetamide - Acid Hydrolysis
Chapter: [14.02] Acid derivatives
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CISCE previous year question papers Class 12 Chemistry (Theory) with solutions 2012 - 2013

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