# Chemistry Shaalaa.com Model Set 1 2020-2021 HSC Science (General) 12th Board Exam Question Paper Solution

Chemistry [Shaalaa.com Model Set 1]
Date: April 2021
Duration: 3h
1. The question paper is divided into four sections.
2. Section A: Q. No. 1 contains Ten multiple-choice type of questions carrying One mark each.
3. Section A: Q. No. 2 contains Eight very short answer type of questions carrying One mark each.
4. Section B: Q. No. 3 to Q. No. 14 contains Twelve short answer type of questions carrying Two marks each. (Attempt any Eight).
5. Section C: Q. No.15 to Q. No. 26 contains Twelve short answer type of questions carrying Three marks each. (Attempt any Eight).
6. Section D: Q.No. 27 to Q. No. 31 contains Five long answer type of questions carrying Four marks each. (Attempt any Three).
7. Use of log table is allowed. Use of calculator is not allowed.
8. Figures to the right indicate full marks.
9. For each MCQ, correct answer must be written along with its alphabet.
e.g., (a) ..... / (b ) .... / ( c ) .... / ( d) ..... Only first attempt will be considered for evaluation.
10. Draw well labeled diagrams and write balanced equations wherever necessary.
11. Given data:
Atomic mass of C = 12, H = 1, O = 16
Atomic number (Z): Mn = 25, Fe = 26, Ce = 58, Ar = 18,
R = 8.314 J K-1 mol-1 or 0.083 L bar K-1 mol-1

Section A
[10]1 | Select and write the correct answer:
[1]1.i

Bottom ash of thermal power stations can be used as raw material for cement and brick industry. This example illustrates which of the following principle of green chemistry?

Atom economy.

Designing safer chemicals.

Design for energy efficiency.

Prevention of waste or by products.

Concept: Principles of Green Chemistry
Chapter: [0.16] Green Chemistry and Nanochemistry
[1]1.ii

The sugar component of nucleotide unit in RNA is _________________

α-deoxy-D-ribose

D-ribose

L-ribose

2-deoxy-L-ribose

Concept: Nucleic Acids
Chapter: [0.14] Biomolecules
[1]1.iii

The theory which explain amphoteric nature of water is ______.

Arrhenius theory

Lewis theory

Ostwald theory

Bronsted-Lowry theory

Concept: Acids and Bases
Chapter: [0.03] Ionic Equilibria
[1]1.iv

The charge on metal ion in [Fe(CN)6]4− is _________

+2

+3

+4

+5

Concept: Terms Used in Coordination Chemistry
Chapter: [0.09] Coordination Compounds
[1]1.v

An intensive property amongst the following is ______.

Mass

Volume

Number of moles

Temperature

Concept: Terms Used in Thermodynamics
Chapter: [0.04] Chemical Thermodynamics
[1]1.vi

Acidic strength of halogen acids increases in the order of _______.

HF > HCl > HBr > HI

HCl > HF > HBr > HI

HBr > HCl > HF > HI

HI > HBr > HCl > HF

Concept: Chemical Properties of Elements of Groups 16, 17 and 18
Chapter: [0.07] Elements of Groups 16, 17 and 18
[1]1.vii

The following electronic configuration of elements shows highest oxidation state

3d54s2

3d54s1

3d104s2

3d104s1

Concept: Properties of Lanthanoids
Chapter: [0.08] Transition and Inner Transition Elements
[1]1.viii

Which of the following is the product of reaction of ethane nitrile with Grignard reagent followed by acid hydrolysis?

a ketone

an aldehyde

an acid

an acid chloride

Concept: Introduction of Aldehydes, Ketones and Carboxylic Acids
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids [12.01] Aldehydes and Ketones
[1]1.ix

The pKb of weak base BOH [Kb(BOH) = 1 × 10-5] will be ______.

-5

5

1

10-5

Concept: Ionic Equilibria - Buffer Solutions
Chapter: [0.03] Ionic Equilibria
[1]1.x

Sodium crystallizes in bcc structure. If the edge length of unit cell is 4.3 × 10-8 cm, the radius of Na atom is ______.

1.86 × 10-8 cm

1.52 × 10-8 cm

2.15 × 10-8 cm

4.3 × 10-8 cm

Concept: Classification of Crystalline Solids
Chapter: [0.01] Solid State [0.01] Solid State
[1]2.i

Name the catalyst used to manufacture of H2SO4 by contact process.

Concept: Characteristic Features of Nanoparticles
Chapter: [0.16] Green Chemistry and Nanochemistry
[1]2.ii

Label the one conjugate acid-base pair in the following reaction.

$\ce{CO^{2-}_{3(aq)} + H2O_{(l)} ⇌ OH^- + HCO^-_3}$

Concept: Acids and Bases
Chapter: [0.03] Ionic Equilibria
[1]2.iii

Write the type of isomerism exhibited by [Co(NH3)5(NO2)]2+ and [Co(NH3)5ONO]2+ pair of complex ion.

Concept: Isomerism in Coordination Compounds
Chapter: [0.09] Coordination Compounds
[1]2.iv

Complete the following reaction:

$\ce{SO_{2(g)} + Cl_{2(g)} ->[Charcoal]}$ ?

Concept: Oxygen and Compounds of Oxygen
Chapter: [0.07] Elements of Groups 16, 17 and 18
[1]2.v

Write the order of ionic character of halides with monovalent metal (M).

Concept: Chemical Properties of Elements of Groups 16, 17 and 18
Chapter: [0.07] Elements of Groups 16, 17 and 18
[1]2.vi

Write formula to calculate magnetic moment.

Concept: Trends in Atomic Properties of the First Transition Series
Chapter: [0.08] Transition and Inner Transition Elements
[1]2.vii

Write chemical formula of ore of zinc.

Concept: Extraction of Metals
Chapter: [0.08] Transition and Inner Transition Elements
[1]2.viii

The vapour pressures of pure liquids A and B are 0.600 bar and 0.933 bar respectively, at a certain temperature.
What is the mole fraction of liquid B in the solution when the total vapour pressure of their mixture is 0.8 bar?

Concept: Vapour Pressure of Solutions of Liquids in Liquids
Chapter: [0.02] Solutions
Section B
[2]3 | Attempt any Eight:

Complete and write the following table

 Reaction Name of catalyst i) Manufacture of HDPE polymer ________________ ii) _______________ V2O5
Concept: Characteristic Features of Nanoparticles
Chapter: [0.16] Green Chemistry and Nanochemistry
[2]4

Write the name of raw material used for preparation of nylon 6, 6 polymer.

Chapter: [0.15] Polymers [0.15] Introduction to Polymer Chemistry
[2]5

Give two points to explain why vapour pressure of solvent is lowered by dissolving nonvolatile solute into it.

Concept: Vapour Pressure Lowering
Chapter: [0.02] Solutions
[2]6

Explain with the help of a potential energy diagram that the catalyst increases the rate of the reaction.

Concept: Integrated Rate Law
Chapter: [0.06] Chemical Kinetics
[2]7

Write one example of each of bidentate and ambidentate ligand.

Concept: Types of Ligands
Chapter: [0.09] Coordination Compounds
[2]8

Define the Standard enthalpy of combustion.

Concept: Thermochemistry
Chapter: [0.04] Chemical Thermodynamics

Define the Enthalpy of sublimation.

Concept: Enthalpies of Physical Transformations
Chapter: [0.04] Chemical Thermodynamics
[2]9

Elements of group 16 have lower ionization enthalpy values compared to those of group 15 elements. Explain why?

Concept: Atomic and Physical Properties of Elements of Group 16, 17 and 18
Chapter: [0.07] Elements of Groups 16, 17 and 18
[2]10

Manganese in the +2 oxidation state is more stable than +3 oxidation state where as iron is stable at +3 oxidation state than +2 oxidation state. Explain why?

Concept: F-block Elements - The Actinoids
Chapter: [0.08] Transition and Inner Transition Elements [8.02] F-block Elements
[2]11

Carboxylic acids have higher boiling points than those of ethers. Give reason.

Concept: Physical Properties
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids
[2]12

What is the action of Grignard reagent on benzonitrile?

Concept: Preparation of Carboxylic Acids
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids
[2]13

Write chemical reaction for the preparation of the following polymer.

polyacrylonitrile

Concept: Polymers - Some Important Polymers
Chapter: [0.15] Polymers [0.15] Introduction to Polymer Chemistry
[2]14

The enthalpy change of the following reaction

$\ce{CH_{4(g)} + Cl_{2(g)} -> CH3Cl_{(g)} + HCl_{(g)}}$

ΔH° = –104 kJ. Calculate C – Cl bond enthalpy.

The bond enthalpies are

 Bond C − H Cl − Cl H − Cl ∆H°/kJ mol−1 414 243 431
Concept: Thermochemistry
Chapter: [0.04] Chemical Thermodynamics
Section C
[3]15 | Attempt any Eight:

Write a chemical reaction to convert glucose into glucose cyanohydrin.

Concept: Carbohydrates
Chapter: [0.14] Biomolecules
[3]16

Derive the equation which implies that the degree of dissociation of weak acid is inversely proportional to the square root of its concentration.

Concept: Types of Electrolyte
Chapter: [0.03] Ionic Equilibria
[3]17

Compound ‘A’ with molecular formula C6H5Cl is fused with NaOH at high temperature under pressure to give compound ‘B’. Compound ‘B’ on treatment with dil.HCl gives compound C having characteristic carbolic odour. Write the chemical equations in support of this. Name the process and give uses of compound C.

Concept: Uses of Alcohols, Phenols and Ethers
Chapter: [0.11] Alcohols, Phenols and Ethers
[3]18

Calculate "E"_"cell"^circ of the following galvanic cell:

Mg(s) / Mg2+(1 M) // Ag+ (1 M) / Ag(s) if "E"_"Mg"^circ = – 2.37 V and "E"_"Ag"^circ = 0.8 V. Write cell reactions involved in the above cell. Also mention if cell reaction is spontaneous or not.

Concept: Electrode Potential and Cell Potential
Chapter: [0.05] Electrochemistry
[3]19

Draw the geometrical isomers of the following complexes [Pt(NH3)(H2O)Cl2] and [Co(NH3)4Cl2]+

Concept: Isomerism in Coordination Compounds
Chapter: [0.09] Coordination Compounds
[3]20

An organic compound A with molecular formula C4H10O on treatment with phosphorus pentachloride gives alkyl chloride. Alkyl chloride on treatment with Mg in presence of dry ether gives a highly reactive compound B.
Compound B reacts with water to give hydrocarbon C. Alkyl chloride on treatment with Na in dry ether as a solvent gives alkane, 2,2,3,3-tetramethylbutane. Identify ‘A’, ‘B’, ‘C’

Concept: Uses and Environmental Effects of Some Polyhalogen Compounds
Chapter: [0.1] Halogen Derivatives
[3]21

Derive the expression for work done in chemical reaction. Write the relationship between ∆H and ∆U for an isochoric process.

Concept: Chemical Thermodynamics
Chapter: [0.04] Chemical Thermodynamics
[3]22

What is the oxidation state of sulfur in the following?

Sulfurous acid

Concept: Oxoacids
Chapter: [0.07] Elements of Groups 16, 17 and 18

What is oxidation state of sulfur in the following?

Sulfuric acid

Concept: Oxoacids
Chapter: [0.07] Elements of Groups 16, 17 and 18

What is oxidation state of sulfur in the following?

Peroxymonosulfuric acid

Concept: Oxoacids
Chapter: [0.07] Elements of Groups 16, 17 and 18
[3]23

What are rare earth elements?

Concept: Properties of f-block Elements
Chapter: [0.08] Transition and Inner Transition Elements

Write any two properties actinides.

Concept: Applications of Actinoids
Chapter: [0.08] Transition and Inner Transition Elements

Write any two uses of actinides.

Concept: Applications of Actinoids
Chapter: [0.08] Transition and Inner Transition Elements
[3]24

What is the action of following reagents on ethanoic acid?

SOCl2/heat

Concept: Aldehydes and Ketones - Preparation of Aldehydes and Ketones
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids [12.01] Aldehydes and Ketones

What is the action of following reagents on ethanoic acid?

sodalime/heat

Concept: Aldehydes and Ketones - Preparation of Aldehydes and Ketones
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids [12.01] Aldehydes and Ketones

What is the action of following reagents on ethanoic acid?

P2O5/heat

Concept: Aldehydes and Ketones - Preparation of Aldehydes and Ketones
Chapter: [0.12] Aldehydes, Ketones and Carboxylic Acids [12.01] Aldehydes and Ketones
[3]25

A solution containing 3 g of solute A (M = 60 g/mol) in 1 L solution is isotonic with a solution containing 8.55 g of solute B in 500 mL solution. What is the molar mass of B?

Concept: Relative Molecular Mass of Non-volatile Substances - Boiling Point Elevation
Chapter: [0.02] Solutions
[3]26

What is the action of following on phenol at low temperature?

1. dil. HNO3
2. conc. H2SO4
3. Br2/CS2
Concept: Alcohols and Phenols
Chapter: [0.11] Alcohols, Phenols and Ethers
Section D
[4]27 | Attempt any Three:
[2]27.i

What is dehydrohalogenation? State the rule for the formation of the preferred product of dehydrohalogenation.

Concept: Preparation, Properties and Uses of Propane-1, 2, 3 Triol - Chemical Properties
Chapter: [0.1] Halogen Derivatives
[2]27.ii

Write the equations for the preparation of ethyl chloride using

1. Hydrogen halide
2. ethene
3. Thionyl chloride

Which of these methods is preferred and why?

Concept: Uses and Environmental Effects of Some Polyhalogen Compounds
Chapter: [0.1] Halogen Derivatives
[4]28

Calculate the voltage of the cell Sn(s) / Sn2+(0.02 M) // Ag+ (0.01 M) / Ag(s) at 25 °C.

Given: "E"_"Sn"^circ = - 0.136, "E"_"Ag"^circ = 0.800 V

Concept: Electrode Potential and Cell Potential
Chapter: [0.05] Electrochemistry
[4]29

Derive an expression for the relation between half-life and rate constant for first-order reaction.
The half-life period for the first order reaction is 1.7 hrs. How long will it take for 20% of the reactant to disappear?

Concept: Integrated Rate Law
Chapter: [0.06] Chemical Kinetics
[4]30

Derive the relationship between density of substance, its molar mass, and the unit cell edge length. Explain how you will calculate the number of particles, and a number of unit cells in x g of metal.

Concept: Cubic System
Chapter: [0.01] Solid State
[4]31

Write the factors influencing the basicity of amines.

Concept: Basicity of Amines
Chapter: [0.13] Amines

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