# Chemistry Panchkula Set 1 2014-2015 CBSE (Science) Class 12 Question Paper Solution

Chemistry [Panchkula Set 1]
Date: March 2015

[1] 1

Write a method by which lyophobic colloids can be coagulated.

Concept: Classification of Colloids - Classification Based on Nature of Interaction Between Dispersed Phase and Dispersion Medium
Chapter: [0.05] Surface Chemistry
[1] 2

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: [0.01] Solid State
[1] 3

Out of white phosphorus and red phosphorus, which one is more reactive and why?

Concept: P - Block Group 15 Elements - Phosphorus - Allotropic Forms
Chapter: [0.07] P - Block Elements
[1] 4

Write the IUPAC name of the given compound:

Concept: Nomenclature of Coordination Compounds - Naming of Mononuclear Coordination Compounds
Chapter: [0.09] Coordination Compounds
[1] 5

Which would undergo SN1 reaction faster in the following pair and why?

Concept: Hydrocarbons: Alkanes - Reactions of Haloalkanes - Nucleophilic Substitution Reactions
Chapter: [0.1] Haloalkanes and Haloarenes
[2] 6 | Attempt Any One
[2] 6.1

State Henry’s law.

Concept: Solubility - Solubility of a Gas in a Liquid
Chapter: [0.02] Solutions

Why do gases always tend to be less soluble in liquids as the temperature is raised?

Concept: Solubility - Solubility of a Gas in a Liquid
Chapter: [0.02] Solutions
[2] 6.2

State Raoult’s law for the solution containing volatile components

Concept: Vapour Pressure of Liquid - Vapour Pressure of Liquid- Liquid Solutions
Chapter: [0.02] Solutions

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

Concept: Types of Solutions
Chapter: [0.02] Solutions
[2] 7

Following reactions occur at cathode during the electrolysis of aqueous sodium chloride solution:

Na+(aq) + e ⟶ Na (s) E0 =  2.71 V

H+(aq) + e ⟶ 1/2  H2 (g) E0 = 0.00 V

On the basis of their standard reduction electrode potential (E0) values, which reaction is feasible at the cathode and why?

Concept: Electrolytic Cells and Electrolysis - Introduction
Chapter: [0.03] Electrochemistry

Why does the cell potential of mercury cell remain constant throughout its life?

Concept: Batteries - Primary Batteries
Chapter: [0.03] Electrochemistry
[2] 8

Why do the transition elements have higher enthalpies of atomisation?

Concept: General Properties of the Transition Elements (D-block)
Chapter: [0.08] "D" and "F" Block Elements

In 3d series (Sc to Zn), which element has the lowest enthalpy of atomisation and why?

Concept: General Properties of the Transition Elements (D-block)
Chapter: [0.08] "D" and "F" Block Elements
[2] 9

Write down the IUPAC name of the following complex: [Co(NH3)5 (NO2)](NO3)2

Concept: Nomenclature of Coordination Compounds - Naming of Mononuclear Coordination Compounds
Chapter: [0.09] Coordination Compounds

Write the formula for the following complex:Potassium tetracyanidonickelate(II)

Concept: Nomenclature of Coordination Compounds - Formulas of Mononuclear Coordination Entities
Chapter: [0.09] Coordination Compounds
[2] 10

Name the reagents used in the following reactions:

Concept: Preparation of Alcohols from Alkenes, Carbonyl Compounds and Grignard Reagents
Chapter: [0.11] Alcohols, Phenols and Ethers

Name the reagents used in the following reactions:

Concept: Acids - Chemical Reactions of Carboxylic Acids - Reactions Involving Cleavege of C-OH Bond
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids
[3] 11

Calculate the amount of CaCl2 (molar mass = 111 g mol−1) which must be added to 500 g of water to lower its freezing point by 2 K, assuming CaCl2 is completely dissociated. (Kf for water = 1.86 K kg mol−1)

Concept: Colligative Properties and Determination of Molar Mass - Depression of Freezing Point
Chapter: [0.02] Solutions
[3] 12

An element with density 10 g cm−3 forms a cubic unit cell with edge length of 3 × 10−8 cm. What is the nature of the cubic unit cell if the atomic mass of the element is 81 g mol−1?

Concept: Calculations Involving Unit Cell Dimensions
Chapter: [0.01] Solid State
[3] 13

Calculate emf of the following cell at 25°C:

Sn | Sn2+ (0.001 M) || H+ (0.01 M) | H2 (g) (1 bar) | Pt (s)

E_(Sn^(2+)"/"Sn)^0=-0.14V " " E_((H^+"/"H_2))^0=0.00V

Concept: Galvanic Cells - Introduction
Chapter: [0.03] Electrochemistry
[3] 14

Give reasons for the following observations:

Physisorption decreases with increase in temperature.

Chapter: [0.05] Surface Chemistry

Give reasons for the following observations: Addition of alum purifies the water

Concept: Emulsions
Chapter: [0.05] Surface Chemistry

Give reasons for the following observations:

Brownian movement provides stability to the colloidal solution.

Concept: Properties of Colloidal Solutions
Chapter: [0.05] Surface Chemistry
[3] 15

Name the method used for the refining of zirconium.

Concept: Refining
Chapter: [0.06] General Principles and Processes of Isolation of Elements

What is the role of CO in the extraction of Iron?

Concept: Occurrence of Metals
Chapter: [0.06] General Principles and Processes of Isolation of Elements

Reduction of metal oxide to metal becomes easier if the metal obtained is in liquid state. Why?

Concept: Oxidation Reduction
Chapter: [0.06] General Principles and Processes of Isolation of Elements
[3] 16

How would you account for the following:

The chemistry of actinoids is more complicated as compared to lanthanoids.

Concept: F-block Elements - The Actinoids
Chapter: [0.08] "D" and "F" Block Elements

How would you account for the following: Transition metals form complex compounds.

Concept: General Properties of the Transition Elements (D-block)
Chapter: [0.08] "D" and "F" Block Elements

Complete the following equation:

$\ce{2MnO4- + 6H+ + 5NO2- ->}$

Concept: Some Important Compounds of Transition Elements - Oxides and Oxoanions of Metals
Chapter: [0.08] "D" and "F" Block Elements
[3] 17

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

Concept: Isomerism in Coordination Compounds - Stereoisomerism
Chapter: [0.09] Coordination Compounds

On the basis of crystal field theory, write the electronic configuration for d4 ion if Δ0 > P.

Concept: Bonding in Coordination Compounds - Crystal Field Theory (CFT)
Chapter: [0.09] Coordination Compounds

[NiCl4]2− is paramagnetic, while [Ni(CO)4] is diamagnetic, though both are tetrahedral. Why? (Atomic number of Ni = 28)

Concept: Bonding in Coordination Compounds - Magnetic Properties of Coordination Compounds
Chapter: [0.09] Coordination Compounds
[3] 18 | Attempt Any One
[3] 18.1

How do you convert the following: Prop-1-ene to 1-fluoropropane

Concept: Methods of Preparation of Haloalkanes and Haloarenes
Chapter: [0.1] Haloalkanes and Haloarenes

How do you convert the following: Chlorobenzene to 2-chlorotoluene

Concept: Methods of Preparation of Haloalkanes and Haloarenes
Chapter: [0.1] Haloalkanes and Haloarenes

How do you convert the following:

Ethanol to propanenitrile

Concept: Hydrocarbons: Alkanes - Reactions of Haloalkanes - Nucleophilic Substitution Reactions
Chapter: [0.1] Haloalkanes and Haloarenes
[3] 18.2

Write the main products when

n-butyl chloride is treated with alcoholic KOH.

Concept: Hydrocarbons: Alkanes - Reactions of Haloalkanes - Nucleophilic Substitution Reactions
Chapter: [0.1] Haloalkanes and Haloarenes

Write the main products when

2, 4, 6-trinitrochlorobenzene is subjected to hydrolysis

Concept: Chemical Reactions of Phenols (Only)
Chapter: [0.11] Alcohols, Phenols and Ethers

Write the main products when methyl chloride is treated with AgCN.

Concept: Hydrocarbons: Alkanes - Reactions of Haloalkanes - Nucleophilic Substitution Reactions
Chapter: [0.1] Haloalkanes and Haloarenes
[3] 19

Give reasons for the following:

o-nitrophenol is more acidic than o-methoxyphenol.

Concept: Chemical Reactions of Alcohols and Phenols - Reactions Involving Cleavage of O–H Bond
Chapter: [0.11] Alcohols, Phenols and Ethers

Give reasons for the following: Butan-1-ol has a higher boiling point than diethyl ether.

Concept: Physical and Chemical Properties of Alcohols and Phenols
Chapter: [0.11] Alcohols, Phenols and Ethers

Give reasons for the following:

(CH3)3C–O–CH3 on reaction with HI gives (CH3)3C–I and CH3–OH as the main products and not (CH3)3C–OH and CH3–I.

Concept: Hydrocarbons: Alkanes - Reactions of Haloalkanes - Nucleophilic Substitution Reactions
Chapter: [0.1] Haloalkanes and Haloarenes
[3] 20

Predict the products of the following reactions:

Concept: Aldehydes and Ketones - Chemical Reactions of Aldehydes and Ketones - Nucleophilic Addition Reactions
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids

Predict the products of the following reactions:

Concept: Acids - Methods of Preparation of Carboxylic Acids
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids

Predict the products of the following reactions:

Concept: Acids - Chemical Reactions of Carboxylic Acids - Reactions Involving Cleavege of C-OH Bond
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids
[3] 21

Write the names and structures of the monomers of the following polymers: Nylon-6

Concept: Introduction of Polymers
Chapter: [0.15] Polymers

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

Concept: Introduction of Polymers
Chapter: [0.15] Polymers

Write the names and structures of the monomers of the following polymers: Buna-N

Concept: Polymers - Classification of Polymers Based on Mode of Polymerisation
Chapter: [0.15] Polymers
[3] 22

Which one of the following is a polysaccharide:

Starch, Maltose, Fructose, Glucose

Concept: Carbohydrates - Polysaccharides
Chapter: [0.14] Biomolecules

What is the difference between native protein and denatured protein?

Concept: Introduction of Proteins
Chapter: [0.14] Biomolecules

Write the name of the vitamin responsible for the coagulation of blood.

Concept: Introduction of Vitamins
Chapter: [0.14] Biomolecules
[4] 23

Seeing the growing cases of diabetes and depression among young children, Mr Lugani, the principal of one reputed school, organised a seminar in which he invites parents and principals. They all resolved this issue by strictly banning junk food in schools and introducing healthy snacks and drinks like soup, lassi, milk etc. in school canteens. They also decided to make compulsory half an hour of daily physical activities for the students in the health survey in most of the school and discovered a tremendous improvement in the health of the students

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

(iii) What are antidepressant drugs? Give an example.

(iv) Name the sweetening agent used in the preparation of sweets for a diabetic patient.

Concept: Chemicals in Food - Artificial Sweetening Agents and Food Preservatives
Chapter: [0.16] Chemistry in Everyday Life
[5] 24 | Attempt Any One
[5] 24.1

Write the chemical equations involved in the following reactions:(i) Hoffmann-bromamide degradation reaction

Concept: Amines - Preparation of Amines
Chapter: [0.13] Organic Compounds Containing Nitrogen

Illustrate the following reaction giving suitable example in each case: Diazotisation

Concept: Diazonium Salts - Method of Preparation of Diazonium Salts
Chapter: [0.13] Organic Compounds Containing Nitrogen

Illustrate the following reaction giving suitable example in each case:Gabriel phthalimide synthesis

Concept: Amines - Preparation of Amines
Chapter: [0.13] Organic Compounds Containing Nitrogen

Distinguish between the following pairs of compounds: Aniline and N-methylaniline

Concept: Amines - Identification of Primary, Secondary and Tertiary Amines
Chapter: [0.13] Organic Compounds Containing Nitrogen
[5] 24.2

Write the structures of main products when benzene diazonium chloride (C_6H_5N_2^(+)Cl^-)reacts with the following reagents:

CuCN/KCN

Concept: Diazonium Salts - Chemical Reaction of Diazonium Salts - Reactions Involving Displacement of Nitrogen
Chapter: [0.13] Organic Compounds Containing Nitrogen

Write the structures of main products when benzene diazonium chloride (C_6H_5N_2^(+)Cl^-)reacts with the following reagents:

H2O

Concept: Diazonium Salts - Chemical Reaction of Diazonium Salts - Reactions Involving Displacement of Nitrogen
Chapter: [0.13] Organic Compounds Containing Nitrogen

Write the structures of main products when benzene diazonium chloride (C_6H_5N_2^(+)Cl^-)reacts with the following reagents:

CH3CH2OH

Concept: Diazonium Salts - Chemical Reaction of Diazonium Salts - Reactions Involving Displacement of Nitrogen
Chapter: [0.13] Organic Compounds Containing Nitrogen

Arrange the following:

Aniline, p-nitroaniline, p-methylaniline - in the increasing order of their basic strength

Concept: Amines - Chemical Reactions of Amines - Basic Character of Amines
Chapter: [0.13] Organic Compounds Containing Nitrogen
[5] 25 | Attempt Any One
[5] 25.1

What is rate of reaction?

Concept: Rate of a Chemical Reaction
Chapter: [0.04] Chemical Kinetics

Write two factors that affect the rate of reaction.

Concept: Factors Influencing Rate of a Reaction
Chapter: [0.04] Chemical Kinetics

The rate constant of a first order reaction increases from 4 × 10−2 to 8 × 10−2 when the temperature changes from 27°C to 37°C. Calculate the energy of activation (Ea). (log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021)

Concept: Temperature Dependence of the Rate of a Reaction
Chapter: [0.04] Chemical Kinetics
[5] 25.2

For a reaction A + B ⟶ P, the rate is given by

Rate = k [A] [B]2

How is the rate of reaction affected if the concentration of B is doubled?

Concept: Factors Influencing Rate of a Reaction
Chapter: [0.04] Chemical Kinetics

For a reaction A + B ⟶ P, the rate is given by

Rate = k [A] [B]2

What is the overall order of reaction if A is present in large excess?

Concept: Factors Influencing Rate of a Reaction
Chapter: [0.04] Chemical Kinetics

A first order reaction takes 23.1 minutes for 50% completion. Calculate the time required for 75% completion of this reaction.

(log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021)

Concept: Integrated Rate Equations - Half-life of a Reaction
Chapter: [0.04] Chemical Kinetics
[5] 26 | Attempt Any One
[5] 26.1

Account for the following: Interhalogens are more reactive than pure halogens.

Concept: P - Block Group 17 Elements - Interhalogen Compounds
Chapter: [0.07] P - Block Elements

Account for the following:

N2 is less reactive at room temperature.

Concept: Concept of Group 15 Elements
Chapter: [0.07] P - Block Elements

Account for the following: Reducing character increases from NH3 to BiH3.

Concept: Concept of Group 15 Elements
Chapter: [0.07] P - Block Elements

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

Concept: P - Block Group 15 Elements - Oxoacids of Phosphorus
Chapter: [0.07] P - Block Elements

Draw the structures of the following molecules: XeF4

Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
Chapter: [0.07] P - Block Elements
[5] 26.2

which poisonous gas is evolved when white phosphorus is heated with conc. NaOH solution? Write the chemical equation involved.

Concept: P - Block Group 15 Elements - Phosphine
Chapter: [0.07] P - Block Elements

Which noble gas has the lowest boiling point?

Concept: P - Block Group 18 Elements - Concept of Group 18 Elements
Chapter: [0.07] P - Block Elements

Fluorine is a stronger oxidising agent than chlorine. Why?

Concept: P - Block Group 17 Elements - Concept of Group 17 Elements
Chapter: [0.07] P - Block Elements

What happens when

H3PO3 is heated ?

Write the reactions involved.

Concept: P - Block Group 15 Elements - Phosphine
Chapter: [0.07] P - Block Elements

Complete the equation

PbS + O3

Concept: P - Block Group 16 Elements - Ozone
Chapter: [0.07] P - Block Elements

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