Kerala Plus Two Chemistry Board Model Paper 2021 with Answers

Reviewing Kerala Syllabus Plus Two Chemistry Previous Year Question Papers and Answers Pdf Board Model Paper 2021 helps in understanding answer patterns.

Kerala Plus Two Chemistry Board Model Paper 2021 with Answers

Time: 2 Hours
Maximum: 60 Scores

Answer the following questions from 1 to 40 up to a maximum score of 60.
Questions from 1 to 11 carry 2 scores each. (11 × 2 = 22)

Question 1.
Calculate the number of particles present per unit cell in the cubic lattice shown below:

Answer:
bcc
Particles at the corner contribute \(\frac{1}{8}\).
Particles at 8 corners contribute
∴ \(\frac{1}{8}\) × 8 = 1
Particle at the centre contributes one as a whole.
∴ Total no. of particels = 1 + 1 = 2

Question 2.
With the help of a diagram, represent the arrangement of valence band and conduction band in semiconductors and insulators.
Answer:

Question 3.
Classify the following substances into ionic solids and molecular solids.
Answer:

Ionic Solid	Molecular Solid
NaCl, Zinc Sulphide	Ice, Solid NH3

Question 4.
What are isotonic solutions? Give one example.
Answer:
Isotonic solutions are solutions with the same osmotic pressure.
Blood plasma and 0.9% saline solution.

Question 5.
Write any two methods for preventing corrosion of metallic objects.
Answer:
Painting, galvanising, and applying grease.

Question 6.
The rate expression for a reaction is
Rate = k[A]^1/2 [B]^3/2
Calculate
(i) Overall order of reaction. (1)
(ii) Unit of rate constant. (1)
Answer:
(i) Overall order = \(\frac{1}{2}+\frac{3}{2}=\frac{4}{2}\) = 2
(ii) Unit of rate constant for nth order = \(\mathrm{mol}^{1-\mathrm{n}} l^{n-1} \mathrm{~s}^{-1}\)
For second order = \(\mathrm{mol}^{-1} l^1 \mathrm{~s}^{-1}\)

Question 7.
Write any two characteristics of Chemisorption.
Answer:
Chemisorption – Due to chemical bonds, irreversible, specific.

Question 8.
How will you prepare XeF₆? Give its structure.
Answer:

Question 9.
What are interhalogen compounds? Write any one of its uses.
Answer:
Inter halogen compounds are compounds formed by two different halogen atoms.
eg. IF₃, BrF₅, CIF₃, etc.
Uses:

• Used for uranium enrichment
• Are very useful chlorinating agents
• Used as non-aqueous solvents (any one)

Question 10.
Identify the products A and B in the following reaction:

Answer:

Question 11.
Which among CH₃COOH and is more acidic? Give reason.
Answer:
is more acidic due to the presence of an electron withdrawing Cl-group.
-I affect increases acidity.

Questions from 12-29 carry 3 scores each. (18 × 3 = 54)

Question 12.
‘Partial pressure of the gas in vapour phase is proportional to the mole fraction of the gas in solution.’
(i) Name the law stated above. (1)
(ii) Write any two applications of the law. (2)
Answer:
(i) Henry’s law
(ii) Applications of Henry’s law:

• When a soda bottle opens, a fizz sound occurs.
• Scuba divers use a little He dissolved in an oxygen cylinder.

Question 13.
(i) What are ideal solutions? (1)
(ii) A mixture of chloroform and acetone is a non-ideal solution. Identify the type of deviation shown by this mixture and give a reason for it. (2)
Answer:
(i) Ideal solutions – Obey Raoults Law
\(P_A=P^0 A \cdot x_n\)
or
ΔV_mix = 0
or
ΔH_mix = 0
(ii) Negative deviation: Due to the decrease in vapour pressure by the formation of H-bond between acetone and chloroform.

Question 14.
What are primary cells? Write an example for a primary cell and specify its anode and cathode.
Answer:
Primary cell – Can not be recharged or reused.
eg. dry cell, anode – Zn rod, cathode – graphite rod (carbon).

Question 15.
Represent the cell in which the following reaction takes place:

Answer:

Question 16.
Write the expression for the integrated rate equation of a first order reaction and derive the equation for its half-life.
Answer:

Question 17.
(i) What is meant by coagulation of sol? (1)
(ii) Write any two methods used for the coagulation of lyophilic Sols. (2)
Answer:
(i) Accumulation of colloidal particles is called coagulation of the sol.
(ii) By adding an electrolyte of oppositely charged colloidal particles.

Question 18.
(i) Which among the following pres can be concentrated by magnetic separation method? (1)
(A) Bauxite
(B) Haematite
(C) Zinc blende
(D) Calamine
(ii) Explain the hydraulic washing method for the concentration of ore. (2)
Answer:
(i) Haematite
(ii) Crushed ore is washed with running water, i.e., taken in a tank and water is poured. The gauge particles are washed away and heavier metals are left behind.

Question 19.
(i) What are the purposes of adding Na₃AlF₆ to purified alumina in the metallurgy of aluminium? (2)
(ii) Write any two uses of aluminium. (1)
Answer:
(i) To reduce the melting point of Alumina.
(ii) To make utensils, lab reagents.

Question 20.
(i) Explain Mond process for refining nickel. (2)
(ii) Which among the following can be refined by distillation? (1)
(A) Mercury
(B) Copper
(C) Silicon
(D) Zirconium
Answer:
(i)

M is treated with carbon monoxide and nickel tetra carbonyl is formed. It is again strongly heated to get decomposed.
(ii) Mercury

Question 21.
What is meant by lanthanoid contraction? Give its consequences.
Answer:
The steady decrease in atomic and ionic size of atoms from Lanthanum to Lutetium with increase in atomic number is known as Lanthanoid contraction.
Eg. Zr and Hf are similar
Consequences:

• Second and third transition series elements are similar and very difficult to separate.
• The basic strength of the hydroxides decreases from La(OH)₃ to Lu(OH)₃.

Question 22.
(i) Why are the transaction and their compounds used as catalysts? (2)
(ii) Which is the transition metal compound used as catalyst in the contact process? (1)
Answer:
(i) Due to its variable oxidation state and vacant d orbitals.
(ii) V₂O₅

Question 23.
(i) Name the type of structural isomerism exhibited by the following pair. (1)
[CO(NH₃)₅(SO₄)] Br and [Co(NH₃)₅Br] SO₄
(ii) Draw the Geometrical isomers of [Pt(NH₃)₂Cl₂]. (2)
Answer:
(i) Ionisation isomerism
(ii) Geometical isomers of [Pt(NH₃)₂Cl₂] are:

Question 24.
(i) Write the formulae for the following co-ordination compounds: (2)
(A) Tetraamminediaquacobalt (III) chloride
(B) Potassiumtetracyanidonickelate(II)
(ii) Which among the above is a homoleptic complex? (1)
Answer:
(i) A – [Co(H₂O)₂(NH₃)₄]Cl₃
B – K₂[Ni(CN)₄]
(ii) Potassiumtetracyanidonickelate (II) or K₂[Ni(CN)₄] is homoleptic since it contains only one type of ligand.

Question 25.
(i) Describe the preparation of ethanol from molasses. (2)
(ii) What is meant by denaturation of alcohol? (1)
Answer:

(ii) Ethanol is made unfit to drink by adding a little amount of methanol or pyridine to it. This is known as denaturation of alcohol.

Question 26.
(i) Alcohols have higher boiling points in comparison to hydrocarbons of comparable molar mass. Give reason. (1)
(ii) Arrange the following compounds in the increasing order of their boiling points: (2)
Propanol, Ethanol, Butan-1-ol, Butan-2-ol
Answer:
(i) Due to the presence of hydrogen bond.
(ii) Ethanol < propanol < butan 2-ol < butan 1-ol

Question 27.
(i) Name the type of linkage between the two monosaccharide units through oxygen atom in a disaccharide. (1)
(ii) Write two differences between DNA and RNA. (2)
Answer:
(i) Glycosidic linkage
(ii)

DNA	RNA
1. Deoxyribonucleic acid	1. Ribonucleic acid
2. The nitrogen bases present are (ATCG) Adenine, Thymine, Cytosine, Guanine	2. The nitrogen bases Present are (AUCG) Adenine, Uracil, Cytosine, Guanine

Question 28.
(i) Write the monomers used for getting the following polymers.
(A) Nylon-6
(B) Polystyrene
(ii) Which among the following is a condensation polymer? (1)
(A) Polyethylene
(B) Buna-S
(C) Nylon-6,6
(D) Teflon
Answer:
(i) (A) Nylon-6 – Caprolactam
(B) Polystyrene – Styrene
(ii) Nylon 6, 6

Question 29.
Match the drugs in Column-I with their therapeutic action in Column II.

Column-I	Column-II
(i) Antacid	(A) Neurologically active drugs
(ii) Tranquilliser	(B) Antimicrobial drugs
(iii) Disinfectant	(C) Treatment for acidity

Answer:
(i) Antacid – Treatment for acidity
(ii) Tranquilizer – Neurologically active drug
(iii) Disinfectant – Antimicrobial drugs

Questions from 30-40 carry 4 scores each. (11 × 4 = 44)

Question 30.
Explain the following:
(i) Crystal lattice
(ii) Void
(iii) Frenkel defect
(iv) F-centres
Answer:
(i) Crystal lattice: Three dimensional representation of particles of a crystal.
(ii) Void: The interstitial space in the crystal lattice.
(iii) Due to the absence of a cation from its lattice and is seen in the void. No change in density.
(iv) F centre – Electron trapped anion vacancy.

Question 31.
Solids can be divided into five types based on their response to the magnetic field. Describe any four magnetic properties.
Answer:
1. Ferromagnetic substances: ↑ ↑ ↑ ↑ ↑
Magnetic moments are in the same direction.
eg: Fe, Ni
2. Antiferromagnetic substances: ↑↓ ↑↓ ↑↓
Magnetic moments are in equal and opposite directions.
eg: MnO, NiO, Fe₂O₃
3. Ferrimagnetic substances: ↑↑↑ ↓↓ ↑↓
Magnetic moments are unequal and opposite in direction.
eg: Fe₃O₄, ZnFe₂O₄, MgFe₂O₄
4. Paramagnetic substances are attracted to a magnetic field and are shown by compounds or atoms with an unpaired electron.
eg. O₂, Cu²⁺.

Question 32.
(i) What are colligative properties? (1)
(ii) Name any two colligative properties? (1)
(iii) Calculate the osmotic pressure exerted by a solution prepared by dissolving 1.0 g of a polymer of molar mass 18500 g mol^-1 in 450 mL of water at 37°C (R = 0.821 L atm k^-1 mol^-1) (2)
Answer:
(i) Colligative properties are those properties which depend only on the number of particles.
(ii) (1) Relative lowering of vapour pressure
(2) Depression in freezing point
(3) Elevation in boiling point
(4) Osmotic pressure

Question 33.
(i) State Kohlrausch law of independent migration of ions. (2)
(ii) \(\Lambda_{\mathrm{m}}^0\) for NaCl, HCl, CH₃COONa are 126.4, 425.9 and 91.0 S cm² mol^-1 respectively. Calculate \(\Lambda_{\mathrm{m}}^0\) for CH₃COOH. (2)
Answer:
Kohlrausch Law
(i) The law states that the limiting molar conductivity of an electrolyte is the sum of the limiting molar ionic conductivities of the cations and anions of the electrolyte present in the solution.
\(\lambda_{\mathrm{m}}^0 \mathrm{NaCl}=\lambda_{\mathrm{Na}^{+}}^0+\lambda_{\mathrm{cl}}^0\)
(ii) \(\lambda_{\mathrm{m}}^0 \mathrm{CH}_3 \mathrm{COOH}=\lambda_{\mathrm{m}}^0 \mathrm{CH}_3 \mathrm{COONa}+\lambda_{\mathrm{m}}^0 \mathrm{HCl}-\lambda_{\mathrm{m}}^0 \mathrm{NaCl}\)
= 91 + 425.9 – 126.4
= 390.5 S cm² mol^-1

Question 34.
Consider the following equation:
K = \(A e^{(-E a / R r)}\)
(i) What does the term ‘A’ represent? (1)
(ii) The rate of a chemical reaction doubles when temperature is increased from 300K to 310K. Calculate the activation energy. (3)
Answer:
(i) A – Arhenius factor

Question 35.
Explain the following:
(i) Lyophilic colloid
(ii) Peptization
(iii) Tyndall effect
(iv) Electrophoresis
Answer:
(i) Lyophillic Colloid: Dispersed phase with very high affinity for dispersion medium.
(ii) Peptization: Conversion of a precipitate to colloid.
(iii) Tyndal effect: Scattering of light by colloidal particles.
(iv) Electrophoresis: Movement of colloidal particles under electric field.

Question 36.
(i) Explain the Ostwald’s process for the preparation of nitric acid. (3)
(ii) Write any two uses of nitric acid. (1)
Answer:
(i) 1. Catalytic oxidation of NH3 to form NO in the presence of platinum.

2. NO is converted to NO₂
2NO + O₂ → 2NO₂
3. NO₂ is treated with water to form HNO₃
NO₂ + H₂O → HNO₃
(ii) (a) Lab reagent
(b) Used for making fertilizers

Question 37.
(i) What are the products obtained when 2-Bromopentane is treated with alcoholic KOH? (2)
(ii) Identify the major product obtained in the above reaction. (1)
(iii) Name the rule that decides the formation of the major product. (1)
Answer:

(ii) Major product is Pent-2-ene / CH₃CH₂CH=CHCH₃
(iii) Saytzef Rule/Zaitsev Rule

Question 38.
Describe the following:
(i) HVZ reaction. (2)
(ii) Cannizaro reaction (2)
Answer:
(i) HVZ reaction: Carboxylic acid with α-hydrogen when treated with chlorine or bromine in the presence of red phosphorous gives α-halo carboxylic acids.

(ii) Cannizaro reaction: Aldehydes or ketones without α-hydrogen undergo oxidation and reduction in presence of conc. alkali to form acid salt and alcohol.

Question 39.
(i) Which among the following reduces Fehling reagent? (1)
(A) Propanone
(B) Benzophenone
(C) Ethanal
(D) Butanone
(ii) Name the class of organic compound obtained when aldehydes undergo reaction with the following reagents: (3)
(A) HCN
(B) Alcohol
(C) Hydroxylamine
Answer:
(i) (C) Ethanal (Aldehydes only gives Fehling’s test)
(ii) (A) Cyanohydrins
(B) Hemiacetal Acetal
(C) Oxime

Question 40.
(i) Which among the following is a primary amine? (1)
(A) (CH₃)₂CHNH₂
(B) C₆H₅NHCH₃
(C) (CH₃)₃N
(D) (CH₃)₂NH
(ii) Explain the reaction of Hinsberg reagent with primary, secondary and tertiary amines.
Answer:
(i) (CH₃)₂ CH NH₂
(ii) Hinsberg reagent- C₆H₅SO₂Cl (Benzene Sulphonyl Chloride)
1° amine + Hinsberg reagent → a precipitate soluble in alkali
2° amine + Hinsberg reagent → a precipitate insoluble in alkali
3° amine + Hinsberg reagent → no reaction