# Chemistry (Theory) 2014-2015 ISC (Commerce) Class 12 Question Paper Solution

Chemistry (Theory)
Date: March 2015

Question 1 is Compulsory

Answer Any 2 Question From Question 2 to Question 4

Answer Any 2 From Question 5 to Question 7

Answer Any 2 From Question 8 to Question 10

[20]1
[5]1.1 | Fill in the blanks by choosing the appropriate word/word from those ·given in the brackets:  (increases, decreases, positive, efficient, 68, non-efficient, no a-hydrogen, α-hydrogen, negative, Rosenmund's, greater, Cannizzaro, 74, common-ion effect, lesser; buffer action, diamagnetic, paramagnetic)
[1]1.1.1

The more _____ the standard reduction potential of a metal, the ____ is its ability to displace hydrogen from acids.

Concept: Galvanic Cells, Mechanism of Current Production in a Galvanic Cell; - Standard Hydrogen Electrode
Chapter: [6.02] Galvanic cells, mechanism of current production in a galvanic cell;
[1]1.1.2

Both ccp and hcp are _________ packings and occupy. about_______ % of the available space.

Concept: States of Matters: Structure and Properties Solid State - Packing in 3 – D
Chapter: [0.02] States of Matters: Structure and Properties Solid State
[1]1.1.3

The solubility of silver chloride _______ in the presence of sodium: chloride because of ___________

Concept: Solubility Product and Its Applications - Solubility product
Chapter: [5.05] Solubility product and its applications
[1]1.1.4

Benzaldehyde undergoes ________ reaction on treatment with concentrated sodium hydroxide because it has _______ atom

Concept: Haloalkanes - Reaction of Haloalkanes with - Aq. Sodium Hydroxide
Chapter: [11.03] Preparation, properties, uses of haloalkanes
[1]1.1.5

The transition metals show _________ character because of the presence of unpaired· electrons and Cu+ is ____________ because of its electronic configuration is [Ar]3d10

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
[5]1.2 | Complete the · following statements by selecting the correct alternative from the choices are given:
[1]1.2.1

The molal freezing point constant of water is 1·86 K kg mol-1. Therefore, the freezing point of 0·1 M NaCl solution in water is expected to be:

1) -1.86°C

2) -0.372 °C

3) -0.186 °C

4) +0.372 °C

Concept: Relative Molecular Mass of Non-volatile Substances - Freezing Point Depression
Chapter: [1.03] Relative molecular mass of non-volatile substances
[1]1.2.2

For a first-order reaction, the rate constant for decomposition of N_2O_5 is 6 xx 10^(-4) sec^(-1).The half-life period for the decomposition in seconds is:

1) 11·55

2) 115·5

3) 1155

4) 1·155

Concept: Order of a Reaction - Mathematical Derivation of Rate Equation for First Order Reaction
Chapter: [3.01] Order of a reaction
[1]1.2.3

When acetaldehyde is treated With Grignard reagent, followed by hydrolysiS-the product formed is:

1) Primary alcohol

2) Secondary alcohol

3) Carboxylic acid

4) Tertiary alcohol

Concept: Acid Derivatives - Reaction with Grignard Reagent
Chapter: [14.02] Acid derivatives
[1]1.2.4

The geometry of XeF6 molecule and_ the hybridization of Xe atom in the molecule.is:

1) Distorted octahedral and sp^3d^3

2) Square planar and sp^3d^2

3) Pyramidal and sp^3

4)Octahedral and sp^3d^3

Concept: Hybridization, Shape and Structure of Compounds
Chapter: [0.08] Chemistry of p-Block Elements: Group 16, 17, 18
[1]1.2.5

In the complexes [Fe(CN)_6]^(3-) and [pt(en) (H_2O)_2(NO_2 (Cl)^(2+)]the respective oxidation numbers of central metal atoms are

1) +3 and +4

2) +6 and + 4

3) +6 and +3

4) +3 and + 3

Concept: Crystal Lattices and Unit Cells - Introduction
Chapter: [0.02] States of Matters: Structure and Properties Solid State
[5]1.3 | Answer the following questions:
[1]1.3.1

What is the effect of temperature on the ionic, product of water? How will it change the pH value of a neutral solution?

Concept: Chemical Kinetics - Effect of Temperature on the Rate Constant of a Reaction
Chapter: [3.04] Effect of temperature on the rate constant of a reaction
[1]1.3.2

How many hours does it take to reduce 3 moles of Fe^(3+)to Fe^(2+) with 2.0 A Current intensity?

Concept: Normality, Molality - Simple Problems Relating Mass, Molar Mass and Mole
Chapter: [1.05] Normality, molality
[1]1.3.3

How is urea prepared by Wohler synthesis?

Concept: Acid Derivatives - Urea Preparation (By Wohler'S Synthesis)
Chapter: [14.02] Acid derivatives
[1]1.3.4

Two liquids A and B form type II non-ideal solution which shows a minimum in its temperature -mole fraction plot (T -x diagram). Can the two liquids be completely separated by fractional distillation?

Concept: Normality, Molality - Normality, Molality, Molarity, Mole Fraction, as Measures of Concentration
Chapter: [1.05] Normality, molality
[1]1.3.5

The aqueous solution of sodium acetate is basic. Explain.

Concept: Ionization of Acids and Bases - Common Ion Effect in the Ionization of Acids and Bases
Chapter: [5.07] Common ion effect
[5]1.4

Match the following:

 1 Disaccharide a Lucas reagent 2 Carbylamine b Condensation polymer 3 Dacron c Obnoxious smell 4 Low spin complex d^2sp^3 d Sucrose 5 Anhydrous ZnCl_2 + conc.HCl e Hexaamminecobalt(III)ion

Concept: Cyanides, Isocyanides and Nitro Compounds
Chapter: [0.15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt
[10]2
[5]2.1
[1]2.1.1

A solution containing 0·5 g of KCl dissolves in 100 g of water and freezes at -0·24°C. Calculate the degree of dissociation of the salt. (Kf for water= 1.86 °C) Atomic weights [K = 39, Cl = 35·5]

Concept: Normality, Molality - Simple Problems Relating Mass, Molar Mass and Mole
Chapter: [1.05] Normality, molality
[1]2.1.2

If 1·71 g of sugar (molar mass = 342) are dissolved in 500 ml of an aqueous solution at 300 K, what will be its osmotic pressure?

Concept: Relative Molecular Mass of Non-volatile Substances - Osmotic Pressure and Its Application in the Determination of Relative Molecular Mass
Chapter: [1.03] Relative molecular mass of non-volatile substances
[1]2.1.3

0·70g of an organic compound, when dissolved in 32g of acetone, produces an elevation of 0·25°C in the boiling point. Calculate the molecular mass of the organic compound (Kb for acetone = 1·72 K kg mol^(-1)).

Concept: Relative Molecular Mass of Non-volatile Substances - Boiling Point Elevation
Chapter: [1.03] Relative molecular mass of non-volatile substances
[4]2.2
[2]2.2.1

What is the difference between the order of a reaction and the molecularity of a reaction?

Concept: Order of a Reaction - Order-reaction (Meaning)
Chapter: [3.01] Order of a reaction
[2]2.2.2

A substance decomposes by following first order kinetics. If 50% of the compound is decomposed in 120 minutes, how long will it take for 90% of the compound to decompose?

Concept: Order of a Reaction - Problems Based on First Order Rate Equation and Half Life Period
Chapter: [3.01] Order of a reaction
[1]2.3

Name the crystal structure of the copper metal.

Concept: Coordination Compounds - Magnetic Characteristics of Coordination Compounds on the Basis of Valence Bond Theory and Crystal Field Theory
Chapter: [0.07] Coordination Compounds
[10]3
[6]3.1
[2]3.1.1

Chromium metal crystallises with a body centred cubic lattice. The edge length of the unit cell is found to be 287 pm. Calculate the atomic radius: What would be the density of chromium in g/cm3? (atomic mass of Cr = 52 ·99)

Concept: States of Matters: Structure and Properties Solid State - Calculation of the Number of Atoms per Unit Cell
Chapter: [0.02] States of Matters: Structure and Properties Solid State
[1]3.1.2

Why does sodium chloride on heating with sodium vapours acquire yellow colour?

Concept: Amorphous and Crystalline Solids
Chapter: [0.02] States of Matters: Structure and Properties Solid State
[1]3.1.3

The equilibrium constant for the reaction:

N_(2(g)) + 3H_(2(g)) ⇌ 2NH_(3(g)) at 715 K, is 6.0 xx 10^(-2)

If, in a particular reaction, there ate 0·25 mol L-1 of H2. and 0·06 mol L-1 of NH3 present, calculate the concentration of N2 at equilibrium

Concept: Reversible Reactions and Dynamic Equilibrium - Equilibrium Constant in Terms of Partial Pressures Kp
Chapter: [4.01] Reversible reactions and dynamic equilibrium
[1]3.1.4

Calculate the concentration of OH- ions in solution when [H+] = 6.2 x 10-2L mol L-1.

Concept: Chemical Kinetics - Effect of Concentration of Reactants on the Rate of a Reaction
Chapter: [3.1] Effect of concentration of reactants on the rate of a reaction
[1]3.1.5

State the Le Chatelier's principle.

Concept: Le Chatelier’S Principle and Its Applications to Chemical Equilibria - Le Chatelier’s Principle
Chapter: [4.02] Le Chatelier’s Principle and its applications to chemical equilibria
[2]3.2

For a crystal of sodium chloride, state:

1) The type of lattice in which it crystallises

2) The coordina~ion number of each sodium ion and chloride ion in the crystal lattice.

3) The number of sodium ions and chloride ions present in a unit cell of sodium chloride.

4) The structural arrangement of the sodium chloride crystaL

Concept: Crystal Lattices and Unit Cells - Introduction
Chapter: [0.02] States of Matters: Structure and Properties Solid State
[2]3.3

Consider the following reaction:

N_2O_(4(g)) + Heat ⇌ 2NO_(2(g))

How is the Composition of equilibrium mixture affected by:

1) a change in temperature

2) a change in pressure

3) change in concentration of N2O4

Concept: Reversible Reactions and Dynamic Equilibrium - Characteristics of Equilibrium Constant
Chapter: [4.01] Reversible reactions and dynamic equilibrium
[10]4
[3]4.1

The specific conductance of a 0.01 M solution of acetic acid at +98 K is 1.65 x 10-4 ohm cm-1. The molar conductance at infinite dilution for H+ ion and CH3COO- ion is 349.1 ohm-1 cm2mol-1 and 40.9 ohm-1 cm2mol-1 respectively.

Calculate:

1) Molar conductance of the solution.

2) The degree of dissociation of CH3COOH.

3) A dissociation constant for acetic acid

Concept: Electrolytic Conductance - Measuring of Molar and Equivalent Conductance
Chapter: [6.04] Electrolytic conductance [6.04] Electrolytic conductance
[4]4.2
[2]4.2.1

Calculate the e.m.f of the following cell reaction at 298 K:

Mg_(s) + Cu^(2+) (0.0001 M) -> Mg^(2+) (0.0001M) + Cu_(s)

The standard potential (E^@)of the cell is  2.71 V

Concept: Galvanic Cells, Mechanism of Current Production in a Galvanic Cell; - Mechanism of Production of Electric Current in a Galvanic Cell
Chapter: [6.02] Galvanic cells, mechanism of current production in a galvanic cell;
[2]4.2.2

The solubility product (Ksp) of BaSO4 is 1.5 X 10-9.Calculate the solubility of barium sulphate in pure water and in 0.1 M BaCl2.

Concept: Solubility - Solubility of a Gas in a Liquid
Chapter: [1.01] Raoult's law and colligative properties
[3]4.3 | Explain the following :
[2]4.3.1

When NH4 Cl and NH4OH are added to a solution containing both, Fe3+ and Ca2+ ions, which ion is precipitated first and why?

Concept: Ionic Equilibria - Buffer Solutions
Chapter: [5.04] Buffer solutions
[1]4.3.2

Dissociation of H2S is suppressed in acidic medium.

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
[5]5
[1]5.1

Write the IUPAC names of the following coordination compounds:

[Cr(NH3)4(H2O)2]Cl3

Concept: Definitions of Some Important Terms Pertaining to Coordination Compounds
Chapter: [0.07] Coordination Compounds

Write the IUPAC names of the following coordination compounds:

[PtCl_2(NH_3)_4][PtCl_4]

Concept: Definitions of Some Important Terms Pertaining to Coordination Compounds
Chapter: [0.07] Coordination Compounds
[1]5.2

State the hybridization and magnetic property of [Fe(CN)6]3- ion according to the valence bond theory.

Concept: Coordination Compounds - Magnetic Characteristics of Coordination Compounds on the Basis of Valence Bond Theory and Crystal Field Theory
Chapter: [0.07] Coordination Compounds
[3]5.3
[2]5.3.1

What type of isomers are [Co(NH_3)_5Br]SO_4and [Co(NH_3)_5SO_4]Br?. Give a  chemical test to distinguish between them.

Concept: Isomerism in Coordination Compounds - Stereoisomerism
Chapter: [0.07] Coordination Compounds
[1]5.3.2

Write the structures of optical isomers of the complex ion [Co(en)_2Cl_2]^+`

Concept: Isomerism in Coordination Compounds - Stereoisomerism
Chapter: [0.07] Coordination Compounds
[5]6
[3]6.1

Give balanced chemical equations for Fluorine is passed through cold, dilute NaOH solution

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

Give balanced chemical equations for  Hydrogen peroxide is treated with an acidified KMnO4 solution.

Concept: Ozone - Hydrogen Peroxide
Chapter: [0.09] Preparation/ Manufacture, Properties and Uses of Compounds of Groups 16, 17, – Ozone, Sulphur Dioxide, Sulphuric Acid, Hydrochloric Acid

Give balanced chemical equations for Sulphuric acid is treated with hydrogen sulphide

Concept: P - Block Group 16 Elements - Sulphuric Acid
Chapter: [0.08] Chemistry of p-Block Elements: Group 16, 17, 18 [0.09] Preparation/ Manufacture, Properties and Uses of Compounds of Groups 16, 17, – Ozone, Sulphur Dioxide, Sulphuric Acid, Hydrochloric Acid
[2]6.2

Draw the structure of xenon tetrafluoride molecule and state the hybridization of the central atom and the geometry of the molecule.

Concept: P - Block Group 18 Elements - Formation of Xenon Compounds with Fluorine and Oxygen – Equation
Chapter: [0.08] Chemistry of p-Block Elements: Group 16, 17, 18
[5]7
[3]7.1

Name the important ore of silver. Write all the steps and reactions involved in the Cyanide process for the extraction of silver from its ore.

Concept: Cyanides, Isocyanides and Nitro Compounds
Chapter: [0.15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt
[2]7.2 | Explain the following:

Why do transition metal ions possess a great tendency to form complexes?

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

The paramagnetic character in-3d-transition series elements increases-: up to Mn and then decreases.

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
[10]8
[5]8.1
[1]8.1.1

How can the following conversions be brought about

Glycerol to formic acid

Concept: Carboxylic Acids - Uses of formic acid and acetic acid
Chapter: [14.01] Carboxylic acids
[1]8.1.2

How can the following conversions be brought about:

Chlorobenzene to phenol

Concept: Carboxylic Acids - Uses of formic acid and acetic acid
Chapter: [14.01] Carboxylic acids
[1]8.1.3

How can the following conversions be brought about:

Diethyl ether to ethanol

Concept: Ethers - Physical and Chemical Properties of ether
Chapter: [13.02] Ethers
[2]8.1.4

How can the following conversions be brought about:

Phenol to aniline.

Concept: Acid Derivatives - Acetylation of Ethanol and Aniline
Chapter: [14.02] Acid derivatives
[2]8.2
[1]8.2.1

How is iodoform prepared from ethanol? Give balanced equation.

Concept: Preparation, Properties, and Uses of the Following: Ethyl Bromide, Chloroform, Iodoform, Haloform Reaction
Chapter: [11.05] Preparation, properties, and uses of the following
[1]8.2.2

What.will be the product fonned when chlorobenzene is heated with sodium metal in the presence of dry ether?

Concept: Alcohols, Phenols and Ethers - Nomenclature
Chapter: [12.04] Classification, general formulae, structure and nomenclature [13.02] Ethers
[3]8.3

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

$\ce{CH3COCH3->[Conc.HNO3][(O)]A}$

$\ce{->[SOCl2]B}$

$\ce{->[NH3]C}$

$\ce{->[LiAlH4]D}$

$\ce{->[HNO2]E}$

$\ce{->[CH3COCl]F}$

Concept: Nomenclature of Coordination Compounds - Naming of Mononuclear Coordination Compounds
Chapter: [0.07] Coordination Compounds
[10]9
[3]9.1

Write the equations involved in the following reactions : Reimer – Tiemann reaction

Concept: Chemical Reactions of Phenols (Only)
Chapter: [12.03] Distinction between primary, secondary and tertiary alcohols

Write the chemical equations to illustrate the following name reactions : Rosenmund reduction

Concept: Aldehydes and Ketones - Preparation of Aldehydes
Chapter: [14.02] Acid derivatives

Give ba1anced equations for the following name reactions:

Concept: Acid Derivatives - Hoffmann’s Degradation
Chapter: [14.02] Acid derivatives
[3]9.2

Give of chemical test to distinguish between the following pairs of compounds:

Ethylamine and diethylamine

Concept: Isocyanides - Methods of preparation From primary amines
Chapter: [0.15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt

Give one chemical test to distinguish between the following pairs of compounds

Acetaldehyde and benzaldehyde

Concept: Uses of Aldehydes and Ketones
Chapter: [13.01] Carbonyl compounds
[4]9.3
[2]9.3.1

Arrange the following compounds in the ascending order of their basic strength and give reasons for your answer:

Methylamine, Aniline, Ethylamine, Diethyl ether

Concept: Acid Derivatives - Acetylation of Ethanol and Aniline
Chapter: [14.02] Acid derivatives
[2]9.3.2

Name the monomers and the type of polymerization in each of the following polymers:

Polyester

Concept: Polymers - Polymerisation
Chapter: [0.16] Polymers

Name the monomers and the type of polymerization in each of the following polymers:

Bakelite

Concept: Types of Polymerisation Reactions - Condensation Polymerisation Or Step Growth Polymerisation
Chapter: [0.16] Polymers
[10]10
[3]10.1

An organic compound A with molecular formula C2H7N on reaction with nitrous acid gives a compound B. Bon controlled oxidation gives compound C. C reduces Tollen's -reagent to give silver mirror and D. B reacts with D in the presence of concentrated sulphuric acid to give sweet smelling compound E. Identify A, B, C, D. and E. Give the reaction of C with ammonia

Concept: Aniline - Importance in Synthesis of Other Organic Compounds
Chapter: [0.15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt
[4]10.2

Give balanced equations for the following reactions:

How.will you Convert ethylamine to methylamine?

Concept: Nitro Compounds - Methods of Preparation Nitro Compounds from Primary Amines
Chapter: [0.15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt

Give balanced equations for the following reaction:

What is the effect of denaturation on the structure of proteins?·

Concept: Introduction of Proteins
Chapter: [0.17] Biomolecules – carbohydrates, proteins, enzymes, vitamins and nucleic acids

Give balanced equations for the following reactions:

Name the nitrogen base residues present in DNA

Concept: Introduction of Nucleic Acids
Chapter: [0.17] Biomolecules – carbohydrates, proteins, enzymes, vitamins and nucleic acids
[3]10.3

Give balanced equations for the following reactions:

Aniline is treated with nitrous acid and HCl at the low temperature

Concept: Chlorobenzene - Preparation from Aniline
Chapter: [11.04] Chlorobenzene

Give balanced equations for the following reactions:

Acetyl chloride is treated with ethyl alcohol.

Concept: Acid Derivatives - Acetylation of Alcohol, Ammonia and Amines
Chapter: [14.02] Acid derivatives

Give balanced equations for the following reactions:

Formaldehyde is treated with ammonia.

Concept: Aldehydes and Ketones - Reactions with Ammonia, Hydroxylamine, Hydrazine and Phenyl Hydrazine
Chapter: [13.01] Carbonyl compounds

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