# Chemistry (Theory) 2015-2016 ISC (Arts) Class 12 Question Paper Solution

Chemistry (Theory)
Date & Time: 11th March 2016, 2:00 pm
Duration: 3h

Part I
[20]1
[5]1.a
[1]1.a.i

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

Ideal solutions obey ………. law and they …………. form azeotropic mixtures.

(Henry’s, aldol condensation, absence, do not, ohm, Raoult’s, increases, common ion effect, easily, three, solubility product, ohm-1, two, four, ohm-1, cm2, Cannizzaro, ohm-1 cm-1, zero, decreases, presence)

Concept: Ideal and Non-ideal Solutions
Chapter: [1.01] Raoult's law and colligative properties
[1]1.a.ii

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

Benzaldehyde undergoes ……….. reaction due to ………… of an α-hydrogen atom.

(Henry’s, aldol condensation, absence, do not, ohm, Raoult’s, increases, common ion effect, easily, three, solubility product, ohm-1, two, four, ohm-1, cm2, Cannizzaro, ohm-1 cm-1, zero, decreases, presence)

Concept: Aldehydes and Ketones - Chemical Properties of Benzaldehyde
Chapter: [13.01] Carbonyl compounds
[1]1.a.iii

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

The solubility of silver chloride ……… in the presence of sodium chloride because of ………..

(Henry’s, aldol condensation, absence, do not, ohm, Raoult’s, increases, common ion effect, easily, three, solubility product, ohm-1, two, four, ohm-1, cm2, Cannizzaro, ohm-1 cm-1, zero, decreases, presence)

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

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

The unit of conductance is ………. and that of specific conductance is ………..

(Henry’s, aldol condensation, absence, do not, ohm, Raoult’s, increases, common ion effect, easily, three, solubility product, ohm-1, two, four, ohm-1, cm2, Cannizzaro, ohm-1 cm-1, zero, decreases, presence)

Concept: Electrochemistry - Electrolytic Conductance
Chapter: [6.04] Electrolytic conductance
[1]1.a.v

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

When the concentration of a reactant of the first-order reaction is doubled, the rate becomes ……… times, but for ……….. order reaction, the rate remains the same.

(Henry’s, aldol condensation, absence, do not, ohm, Raoult’s, increases, common ion effect, easily, three, solubility product, ohm-1, two, four, ohm-1, cm2, Cannizzaro, ohm-1 cm-1, zero, decreases, presence)

Concept: Order of a Reaction - Order-reaction (Meaning)
Chapter: [3.01] Order of a reaction
[5]1.b | Complete the following statements by selecting the correct alternative from the choices given:
[1]1.b.i

The electrochemical equivalent is the amount of substance which gets deposited from its solution on passing electrical charge equal to:

96,500 Coulombs

1 Coulomb

60 Coulombs

965 Coulombs

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

The complexion [Ni(CN)4]2- is:

Square planar and diamagnetic

Tetrahedral and Paramagnetic

Square planar and paramagnetic

Tetrahedral and Diamagnetic

Concept: Magnetic Properties
Chapter: [0.02] States of Matters: Structure and Properties Solid State
[1]1.b.iii

Wohler’s synthesis is used for the preparation of:

Glycine

Amino acids

Urea

Proteins

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

When SO2 gas is passed through the acidified K2Cr2O7 solution, the colour of the solution changes to:

Red

Black

Orange

Green

Concept: P - Block Group 16 Elements - Sulphur Dioxide
Chapter: [0.08] Chemistry of p-Block Elements: Group 16, 17, 18
[1]1.b.v

In the equation $\ce{CH3COOH + Cl2 ->[Red P][-HCl]A , the compound A is :}$

CH3CH2Cl

ClCH2COOH

CH3Cl

CH3COCl

Concept: F-block Elements - Compounds Agno3, Kmno4
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.c | Answer the following questions:
[1]1.c.i

What is the order of reaction whose rate constant has the same unit as the rate of reaction?

Concept: Order of a Reaction - Order-reaction (Meaning)
Chapter: [3.01] Order of a reaction
[1]1.c.ii

What is the pH value of a solution whose hydroxyl ion concentration is 1 × 10-2 M?

Concept: Ionic Equilibria - Multistage Ionization of Acids and Bases with Examples
Chapter: [5.02] Ionic product of water, pH of solutions and pH indicators
[1]1.c.iii

Calculate the number of coulombs required to deposit 5.4 g of Al when the electrode reaction
is: Al3 + 3e + Al [Atomic Weight of Al 27 g/mol].

Concept: Collision Theory of Chemical Reactions
Chapter: [3.02] Collision Theory [3.04] Effect of temperature on the rate constant of a reaction
[1]1.c.iv

Write the reaction to prepare acetaldehyde from hydrogen gas and acid chloride.

Concept: Aldehydes and Ketones - Difference Between Formaldehyde and Acetaldehyde
Chapter: [13.01] Carbonyl compounds
[1]1.c.v

The edge length of the unit cell of a body-centred cubic (bcc) crystal is 352 pm. Calculate the radius of the atom.

Concept: States of Matters: Structure and Properties Solid State - Concept of Radius, Edge Length and Nearest Neighbour Distance
Chapter: [0.02] States of Matters: Structure and Properties Solid State
[5]1.d

Match the following:

 (i) Weak electrolyte (a) the pH of a solution (ii) Colour in crystals (b) Iodoform (iii) Acetone (c) Tollen’s reagent (iv) Sorensen (d) Ostwald dilution law (v) Ammoniacal silver nitrate (e) F – centre
Concept: Ionic Equilibria - Strength of Acids and Bases Based on Their Dissociation Constant
Chapter: [5.06] Ostwald’s dilution law and its derivation
Part II Section A
[50]2 | (Answer the two questions)
[5]2.a
[2]2.a.i

A10% aqueous solution of cane sugar (mol. wt. 342) is isotonic with 1.754% aqueous solution of urea. Find the molecular mass of urea.

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

The molecular weight of an organic compound is 58 g mol-1. What will be the boiling point of a solution containing 48 grams of the solute in 1200 grams of water?
[Kb for water = 0.513°C kg mole-1; Boiling point of water = 100°C]

Concept: Relative Molecular Mass of Non-volatile Substances - Boiling Point Elevation
Chapter: [1.03] Relative molecular mass of non-volatile substances
[1]2.a.iii

What will be the value of Van’t Hoff factor (i) of benzoic acid if it dimerises in aqueous solution? How will the experimental molecular weight vary as compared to the normal molecular weight?

Concept: Relative Molecular Mass of Non-volatile Substances - Determination of Relative Molecular Mass
Chapter: [1.03] Relative molecular mass of non-volatile substances
[4]2.b
[2]2.b.i

Determine the pH value of 0.001 M acetic acid solution if it is 2% ionised at this concentration. How can the degree of dissociation of this acetic acid solution be increased?

Concept: Ionic Equilibria - Multistage Ionization of Acids and Bases with Examples
Chapter: [5.02] Ionic product of water, pH of solutions and pH indicators
[2]2.b.ii

The solubility product of PbCl2 at 298K is 1.7 × 10-5. Calculate the solubility of PbCl2 in g/lit. at 298K.
Atomic Weights: [Pb = 207 and Cl = 35.5]

Concept: Solubility - Solubility of a Gas in a Liquid
Chapter: [1.01] Raoult's law and colligative properties
[1]2.c

Graphite is anisotropic with respect to the conduction of electric current. Explain.

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;
[10]3
[4]3.a
[2]3.a.i

In a body centred and face centred arrangement of atoms of an element, what will be the number of atoms present in respective unit cells? Justify your answer with a calculation.

Concept: Relative Molecular Mass of Non-volatile Substances - Relative Molecular Mass of Non-volatile Substances
Chapter: [1.03] Relative molecular mass of non-volatile substances
[2]3.a.ii

A compound AB has a simple cubic structure and has molecular mass 99. its density is 3.4 g cm-3. What will be the edge length of the unit cell?

Concept: Relative Molecular Mass of Non-volatile Substances - Relative Molecular Mass of Non-volatile Substances
Chapter: [1.03] Relative molecular mass of non-volatile substances
[4]3.b
[2]3.b.i

For the reaction :

$\ce{2NO_{(g)} ⇌ N2_{(g)} + O2_{(g)}}$;

ΔH = -heat

K= 2.5 × 10at 298K

What will happen to the concentration of Nif :

(1) Temperature is decreased to 273 K.

(2) The pressure is reduced

Concept: Vapour Pressure of Liquid Solutions - Vapour Pressure of Liquid- Liquid Solutions
Chapter: [1.01] Raoult's law and colligative properties
[2]3.b.ii

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

(1) The half-life period of the reaction.

(2) The time required for completing 87.5% of the reaction.

Concept: Order of a Reaction - Characteristics of First Order Reaction
Chapter: [3.01] Order of a reaction
[2]3.c

Water acts as Bronsted acid as well as a Bronsted base. Give one example each to illustrate this statement.

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
[10]4
[3]4.a

i)

Consider the following cell reaction at 298 K: [3]
2Ag+ + Cd → 2Ag + Cd2+
The standard reduction potentials (E°) for Ag+/Ag and Cd2-/Cd are 0.80 V and -0.40 V respectively:
(1) Write the cell representation.
(2) What will be the emf of the cell if the concentration of Cd2+ is 0.1M and that of Ag+ is 0.2 M?
(3) Will the cell work spontaneously for the condition given in (2) above?

(ii)

What is a buffer solution? How is it prepared? Explain the buffer action of a basic buffer with a suitable example.

Concept: Crystal Lattices and Unit Cells - Introduction
Chapter: [0.02] States of Matters: Structure and Properties Solid State
[2]4.b

Explain the following:

(i) When NaCl is added to the AgNO3 solution, a white precipitate is formed.
(ii) An aqueous solution of ammonium chloride is acidic in nature.

Concept: Ionization of Acids and Bases - Common Ion Effect in the Ionization of Acids and Bases
Chapter: [5.07] Common ion effect
[3]4.c

A 0.05 M NH4OH solution offers the resistance of 50 ohms to a conductivity cell at 298 K. If the cell constant is 0.50 cm-1 and molar conductance of NH4OH at infinite dilution is 471.4 ohm-1 cm2 mol-1, calculate:
(i) Specific conductance
(ii) Molar conductance
(iii) Degree of dissociation

Concept: Electrochemistry - Electrolytic Conductance
Chapter: [6.04] Electrolytic conductance
Section B
[5]5 | Answer any two questions
[2]5.a

Write the IUPAC names of the following:

(i) [CO(NH3)4SO4]NO3

(ii) K[Pt(NH3)Cl3]

Concept: The Nomenclature of Aliphatic Compounds Containing Halogen Atom - Iupac System for Mono, Di and Tri-halo Derivatives
Chapter: [11.02] The nomenclature of aliphatic compounds containing halogen atom
[1]5.b

What type of isomerism is exhibited by the following pairs of compounds:
(i)  [PtCl2(NH3)4]Br2 and [PtBr2(NH3)4]Cl2
(ii) [Cr(SCN)(H2O)5]2+ and [Cr(NCS)(H2O)5]2+

Concept: Coordination Compounds - Study of Oxidation State of an Element in a Complex
Chapter: [0.07] Coordination Compounds
[2]5.c

How does K2[PtCl4] get ionised when dissolved in water? Will it form a precipitate when AgNO3 solution is added to it? Give a reason for your answer.

Concept: Ionization of Acids and Bases - Common Ion Effect in the Ionization of Acids and Bases
Chapter: [5.07] Common ion effect
[5]6
[3]6.a

Give balanced equations for the following reactions:

(i) Silver nitrate is added to the dilute solution of sodium thiosulphate.
(ii) Potassium dichromate is treated with acidified ferrous sulphate solution.
(iii) Phosphorus reacts with cone, sulphuric acid.

Concept: Order of a Reaction - Relation Between Order and Stoichiometric Coefficients in Balanced Equations
Chapter: [3.01] Order of a reaction
[2]6.b

How will you obtain pure potassium permanganate (KMnO4) crystals from its ore, pyrolusite? Give the steps involved and the reactions.

Concept: Crystal Lattices and Unit Cells - Introduction
Chapter: [0.02] States of Matters: Structure and Properties Solid State
[5]7
[3]7.a

(i)

Sulphur dioxide acts as an oxidizing agent as well as a reducing agent. Give one reaction each to show its oxidizing nature and its reducing nature.
(ii)

Explain why an aqueous solution of potassium hexacyanoferrate (II) does not give the test for ferrous ion.

Concept: Hydrogen Peroxide - Oxidising Properties
Chapter: [0.09] Preparation/ Manufacture, Properties and Uses of Compounds of Groups 16, 17, – Ozone, Sulphur Dioxide, Sulphuric Acid, Hydrochloric Acid
[2]7.b

What is meant by Lanthanide contraction? Write the general electronic configuration of inner transition elements.

Concept: F-block Elements - The Lanthanoids
Chapter: [0.1] Chemistry of Transition and Inner-Transition Elements: d-Block: 3d, 4d and 5d series f-Block: 4f and 5f series
Section C
[10]8 | Answer any two questions :
[5]8.a
[1]8.a.i

How can the following conversions be brought about:

Acetaldehyde to acetaldehyde phenyl hydrazone.

Concept: Aldehydes and Ketones - Difference Between Formaldehyde and Acetaldehyde
Chapter: [13.01] Carbonyl compounds
[1]8.a.ii

How can the following conversions be brought about:

Benzoic acid to aniline.

Concept: Benzoic Acid - Physical Properties of Benzoic Acid
Chapter: [14.01] Carboxylic acids
[2]8.a.iii

How can the following conversions be brought about:

Methyl chloride to acetone.

Concept: Polyhalogen Compounds
Chapter: [11.04] Chlorobenzene
[1]8.a.iv

How can the following conversions be brought about:

Benzene to benzene diazonium chloride.

Concept: Aldehydes and Ketones - Chemical Properties of Benzaldehyde
Chapter: [13.01] Carbonyl compounds
[2]8.b
[1]8.b.i

Glycerol (propane 1,2,3 triol) is more viscous than ethylene glycol (ethane 1,2, diol). Explain

Concept: Oxalic Acid - Oxalic Acid: Preparation from Glycol and Sodium Formate
Chapter: [14.01] Carboxylic acids
[1]8.b.ii

How can urea be detected by the Biuret test?

Concept: Acid Derivatives - Urea Preparation (By Wohler'S Synthesis)
Chapter: [14.02] Acid derivatives
[3]8.c
[1.5]8.c.i

Identify the compounds A,B and C :

$\ce{C2H5OH->[PCl5]A->[KCN]B->[H3O+]C2H5COOH->[NH3][\Delta]C}$

Concept: Preparation, Properties, and Uses of the Following: Ethyl Bromide, Chloroform, Iodoform, Haloform Reaction
Chapter: [11.05] Preparation, properties, and uses of the following
[1.5]8.c.ii

Identify the compound A,B and C:

$\ce{C6H5COOH->[SOCl2]A->[NH3]B->[Br2/KOH]C}$

Concept: Preparation, Properties, and Uses of the Following: Ethyl Bromide, Chloroform, Iodoform, Haloform Reaction
Chapter: [11.05] Preparation, properties, and uses of the following
[10]9
[3]9.a
[1]9.a.i

Give a balanced equation for the following name reaction :

Benzoin condensation

Concept: Aldehydes and Ketones - Benzoin Condensation
Chapter: [13.01] Carbonyl compounds
[1]9.a.ii

Give a balanced equation for the following name reaction :

Wurtz-fitting reaction

Concept: Chlorobenzene - Wurtz-fittig Reaction
Chapter: [11.04] Chlorobenzene
[1]9.a.iii

Give a balanced equation for the following name reaction:

Carbylamine reaction

Concept: Amines - Chemical Reactions of Amines - Carbylamine Reaction
Chapter: [0.15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt
[3]9.b
[1.5]9.b.i

Give the chemical test to distinguish:

Formaldehyde and acetaldehyde

Concept: Aldehydes and Ketones - Difference Between Formaldehyde and Acetaldehyde
Chapter: [13.01] Carbonyl compounds
[1.5]9.b.ii

Give the chemical test to distinguish:

Dimethyl ether and ethyl alcohol.

Concept: General Formula and Structure
Chapter: [13.02] Ethers
[4]9.c
[2]9.c.i

Write the structure of three ethers with molecular formula C4H10O.

Concept: General Formula and Structure
Chapter: [13.02] Ethers
[2]9.c.ii

Starting with Grignard’s reagent, how will you prepare propanoic acid?

Concept: Organometallic Compounds - Organometallic Compounds Including Grignard’S Reagent
Chapter: [11.01] Organometallic compounds
[10]10
[3]10.a

An organic compound A has the molecular formula C7H6O. When A is treated with NaOH followed by acid hydrolysis, it gives two products B and C. When B is oxidized, it gives A when A and C are each treated separately with PCl5, they give two different products D and E.

(i) Identify A, B, C, D, and E.
(ii) Give the chemical reaction when A is treated with NaOH and name the reaction.

Concept: Aldehydes and Ketones - Benzoin Condensation
Chapter: [13.01] Carbonyl compounds
[4]10.b | Answer the following :
[2]10.b.i

What do you observe when glucose solution is heated with Tollen’s reagent?

Concept: Carbohydrates - Structures of Glucose
Chapter: [0.17] Biomolecules – carbohydrates, proteins, enzymes, vitamins and nucleic acids
[2]10.b.ii

Name the monomers and the type of polymerisation in each of the following polymers:
(1) Terylene
(2) Polyvinylchloride

Concept: Polymers - Polymerisation
Chapter: [0.16] Polymers
[3]10.c
[1]10.c.i

Give a balanced equation for the following reaction:

Ethylamine with nitrous acid.

Concept: Salt Formation with Nitric Acid
Chapter: [14.02] Acid derivatives
[1]10.c.ii

Give a balanced equation for the following reaction:

Diethyl ether with phosphorus pentachloride.

Concept: General Formula and Structure
Chapter: [13.02] Ethers
[1]10.c.iii

Give a balanced equation for the following reaction:

Aniline with acetyl chloride.

Concept: Aniline - Test for Aniline
Chapter: [0.15] Cyanides, Isocyanides, Nitro compounds, Amines and Diazonium Salt

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