Kerala Plus Two Chemistry Question Paper March 2022 with Answers

Reviewing Kerala Syllabus Plus Two Chemistry Previous Year Question Papers and Answers Pdf March 2022 helps in understanding answer patterns.

Kerala Plus Two Chemistry Previous Year Question Paper March 2022

Time: 2 Hours
Total Scores: 60

Part-I

A. Answer any 5 questions from 1 to 9. Each carries 1 score. (5 × 1 = 5)

Question 1.
Write an ionic compound which can exhibit both Schottky and Frenkel defect.
Answer:
AgBr (Silver Bromide)

Question 2.
Two solutions having same osmotic pressure at a given temperature are called ______________
Answer:
Isotonic Solution

Question 3.
The law that can be used to determine the limiting molar conductivity (λm°) of weak electrolytes is ______________
Answer:
Kohlrausch Law

Question 4.
The unit of rate constant of a first-order chemical reaction is ______________
(a) mol^-1 Ls^-1
(b) s^-1
(b) mol L^-1 s^-1
(d) mol^-2 L² s^-1
Answer:
(b) s^-1

Question 5.
What is the name of the colloidal system in which both the dispersed phase and dispersion medium are liquids?
(a) Emulsions
(b) Gel
(c) Sol
(d) Foam
Answer:
(a) Emulsions

Question 6.
The method used for the concentration of sulphide ores is
(a) Hydraulic washing
(b) Leaching
(c) Magnetic separation
(d) Froth flotation
Answer:
(d) Froth flotation

Question 7.
The reaction which converts benzene diazonium chloride to chlorobenzene using CuCl and HCl is known as ______________
(a) Swarts reaction
(b) Sandmeyer reaction
(c) Finkelstein reaction
(d) Kolbe’s reaction
Answer:
(b) Sandmeyers reaction

Question 8.
Give a reagent to distinguish 1°, 2°, and 3° alcohols.
Answer:
Lucas reagent [Conc. HCl & Anhydrous ZnCl₂]

Question 9.
The galvanic cells which are used to convert the energy of combustion of fuels like hydrogen, methane, etc. into electrical energy are generally called ______________
Answer:
Fuel Cell

B. Answer all questions from 10 to 13. Each carries 1 score. (4 × 1 = 4)

Question 10.
A white precipitate is obtained when aniline reacts with bromine water at room temperature. The chemical name of the precipitate is ______________
Answer:
2,4,6-Tribromoanilihe

Question 11.
Identify the peptide bond among the following:

Answer:
(c) -CO-NH-

Question 12.
Name the polymerization product formed by the condensation reaction between phenol and formaldehyde
(a) Bakelite
(b) Melamine formaldehyde
(c) Nylon
(d) Dacron
Answer:
(a) Bakelite

Question 13.
The artificial sweetener which is used in cold foods and soft drinks is
(a) BHT
(b) Aspartame
(c) Sodium benzoate
(d) Ranitidine
Answer:
(b) Aspartame

Part-II

A. Answer any 2 questions from 14 to 17. Each carries 2 scores. (2 × 2 = 4)

Question 14.
KCl crystals develop violet colour when heated in an atmosphere of potassium vapour. Explain.
Answer:
It is due to the presence of F-centre i.e., electron trapped anion vacancy.

Question 15.
State Henry’s law and mention any one of its applications.
Answer:
The amount of gas dissolved in a liquid is directly proportional to the pressure applied.
\(\frac{x}{m}\) ∝ P
\(\frac{x}{m}\) = K_HP

Application:

1. Soda bottles show a fizz sound while opening.
2. Scuba divers use little helium in oxygen cylinders.

Question 16.
(i) Write the Arrhenius equation. (1)
(ii) How will you obtain the value of activation energy (Ea) from a graphical plot using the Arrhenius equation? (1)
Answer:
(i) k = \(A \cdot e^{-E a / R T}\)

(ii) Activation energy is the product of the slope from the graph and R.

Question 17.
What is lanthanoid contraction? Mention any one of its consequences.
Answer:
The decrease is atomic and ionic size of lanthanides from La to Lu with an increase in atomic number is known as lanthanoid contraction.
Consequences:
1. Zr and Hf are similar
Nb and Ta are similar
or
2. Separation of lanthanoid mixture is difficult.
or
3. Basicity decreases from La(OH)₃ to Lu(OH)₃

B. Answer any 2 questions from 18 to 20. Each carries 2 scores. (2 × 2 = 4)

Question 18.
Why is Cr²⁺ reducing and Mn³⁺ oxidizing when both have a d⁴ configuration?
Answer:
₂₄Cr – 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵
Cr²⁺ – 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁴
₂₅Mn – 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁵
Mn³⁺ – 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁴
Cr²⁺ easily loses one electron and becomes Cr³⁺ then the d⁴ configuration is changed to d³.
i.e. half-filled t2g oxidation occurs and Cr³⁺ acts as a reducing agent.
Mn³⁺ accepts one electron and becomes an Mn²⁺ – d⁵ half-filled orbital extra stable.
Here oxidation number decreases and reduction occurs and acts as an oxidizing agent.

Question 19.
Explain the carbylamine reaction with the equation.
Answer:
Primary amine treated with chloroform in the presence of alkali gives a foul-smelling gas. This is known as the carbonyl amine reaction.
Carbyl amine is methyl isocyanide

Question 20.
CH₃ – NH₂ is more basic than NH₃ while C₆H₅ – NH₂ is less basic than NH₃. Explain.
Answer:
Due to the presence of aromatic benzene ring where delocalization of electron occurs (+R effect).

Part-III

A. Answer any 3 questions from 21 to 24. Each carries 3 scores. (3 × 3 = 9)

Question 21.
Write any three differences between crystalline and amorphous solids. (3)
Answer:

Crystalline	Amorphous
1. Long-range order	1. Short-range order
2. Definite shape	2. no definite shape
3. Definite M.P.	3. M.P varies over a range
4. Anisotropic	4. Isotropic

Question 22.
18g of glucose, C₆H₁₂O₆, is dissolved in 1 kg of water in a saucepan. At what temperature will water boil at 1.013 bar? (3)
(K_b for water is 0.52 K kg mol^-1, boiling point of water = 373.15 K)
Answer:

Boiling point of the solution = 273.15 + 0.052 = 373.202 K

Question 23.
(i) Mention any two factors which influence the rate of a chemical reaction. (1)
(ii) Derive an expression for the half-life of a first-order reaction from its integrated rate equation. (2)
Answer:
(i) The important factors which affect the rate of a chemical reaction are:
Nature of the reactant, temperature, pressure, presence of catalyst, concentration.

Question 24.
(i) Write a suitable method to covert. (1)
CH₃ – CH₂ – Br to CH₃ – CH₂ – I
(ii) Suggest and explain a suitable mechanism for the nucleophilic substitution of tert-butyl bromide with NaOH. (2)
Answer:
(i) Finkelstein Reaction

(ii) S_N1 mechanism or Substitution Nucleophilic unimolecular mechanism. The reaction occurs in two steps:

Step I: Formation of carbocation

Step II: Addition of OH-

B. Answer any 2 questions from 25 to 27. Each carries 3 scores. (2 × 3 = 6)

Question 25.
(i) What are Grignard reagents? (1)
(ii) State the Saytzeff rule and illustrate it with an example. (2)
Answer:
(i) Grignard reagents -Alkyl magnesium halides or R-MgX
(ii) Saytzeff rule – More symmetrical products are favored.

Question 26.
(i) Alcohols and phenols have higher boiling points. Why? (1)
(ii) What is aspirin? How is it prepared from salicylic acid? (2)
Answer:
(i) Due to the presence of hydrogen bond (Intermolecular H-bond)
(ii) Salicylic acid is heated with acetic anhydride in the presence of mineral acid to give acetylsalicylic acid (Aspirin).

Question 27.
(i) Identify A and B in the following reaction

(ii) What is meant by hydroboration-oxidation reaction? Illustrate it with an example. (2)
Answer:
(i)

(ii) Hydroboration: Alkene is treated with diborane followed by oxidation with H₂O₂ in the presence of aqueous alkali to give alcohol. This occurs according to antimarkonikovs rule.

Part-IV

A. Answer any 3 questions from 28 to 31. Each carries 4 scores. (3 × 4 = 12)

Question 28.
(i) What are secondary batteries? (1)
(ii) Write the electrode reactions and the overall cell reaction happening in the tea storage battery when it is in use. (3)
Answer:
(i) Cells that can be recharged and reused are called secondary cells.
(ii) Anode:
Pb + \(\mathrm{SO}_4^{2-}\) → PbSO₄ + 2e^–
Cathode:
PbO₂ + \(\mathrm{SO}_4^{2-}\) + 4H⁺ + 2e^– → PbSO₄ + 2H₂O
Overall reaction:
Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O

Question 29.
(i) Distinguish homogeneous and heterogeneous catalysis. (2)
(ii) Explain the Tyndal effect. Write any one practical application of this effect. (2)
Answer:
(i) Homogeneous Catalysis: Both the reactants and the catalyst are in the same phase.
Heterogeneous Catalysis: The reactants and catalysts are in different phases.
(ii) The  Tyndall effect is the scattering of light due to colloidal particles. The path of the light can be seen.
eg. Ultra microscope.

Question 30.
(i) Write chemical equations involved in the leaching of alumina from bauxite. (3)
(ii) What is the purpose of adding cryolite or CaF₂ into purified Al₂O₃ during the extraction of Al? (1)
Answer:
(i) Leaching of alumina from Bauxite: Powdered bauxite ore is treated with NaOH. Then sodium Aluminate is formed. To this solution, CO₂ gas is passed. Sod, Aluminate is precipitated as hydrated alumina. It is filleted and heated to get pure alumina.

(ii) To decrease the melting point of Alumina cryolite is mixed with it.

Question 31.
(i) What are oligosaccharides? Give an example. (2)
(ii) What is glycogen? (1)
(iii) Explain the chemical constitution of starch. (1)
Answer:
(i) Carbohydrates that give 3 to 10 minor saccharides on hydrolysis are known as Oligosaccharides.
eg. Sugar.
(ii) Carbohydrates stored in animal bodies are known as glycogen.
(iii) Starch contains two components – amylose and amylopectin.

B. Answer any 1 question from 32 to 33. Carries 4 scores. (1 × 4 = 4)

Question 32.
(i) Differentiate between thermoplastics and thermosetting plastics. (2)
(ii) Write the name and structure of the monomer of neoprene. (2)
Answer:
(i)

Thermoplastics	Thermosetting plastics
1. They can be reused.	1. They cannot be reused.
2. They can repeatedly soften on heating and harden on cooling.	2. Upon heating they undergo extensive cross-linking and become infusible.
3. They are linear or long-branched polymers.	3. They are cross-linked or heavily branched polymers.
4. Eg. Polythene	4. Eg. Bakelite

(ii) Neoprene – monomer is chloroprene 2-chiro 1, 3 butadiene

Question 33.
(i) Distinguish anionic detergents and cationic detergents with suitable examples. (3)
(ii) Name any one antioxidant used in food materials. (1)
Answer:
(i)

Anionic Detergents	Cationic Detergents
1. They contain Na salts of sulphonated long-chain alcohols or hydrocarbons.	1. They are quaternary ammonium salts of amines with acetates chlorides or bromides.
2. Anionic part is used in cleaning action.	2. The cationic part is the cause of the cleaning action.
3. Used in toothpaste.	3. Used in Hair conditioner.
4. Sodium Lauryl sulphate or Sod. Dodecyl benzene sulphonate.	4. Cetyl trimethyl ammonium bromide or quarternary ammonium compounds.

(ii) Butylated hydroxy toluene (BHT), Butylated hydroxy anisole (BHA).

Part-V

Answer any 2 questions from 34 to 36. Each carries 6 scores. (2 × 6 = 12)

Question 34.
(i) Write the chemical reaction when PCl₅ is strongly heated. (1)
(ii) What are interhalogen compounds? Give two examples. (2)
(iii) Explain the steps involved in the contact process to manufacture H₂SO₄. (3)
Answer:
(i) When strongly heated PCl₅ decomposes to form PCl₃ and Cl₂.
PCl₅ → PCl₃ + Cl₂
(ii) Two halogens combine to form interhalogen compounds.
eg. BrF₅, CIF₃
(iii) The contact process involves the following steps:
S + O₂ → SO₂
SO₂ + O₂ → SO₃
SO₃ + H₂SO₄ → H₂SO₂O₇ oleum
H₂SO₂O₇ + H₂O → 2H₂SO₄

Question 35.
(i) Draw the geometrical isomers of [Co(NH₃)₄Cl₂]⁺. (2)
(ii) Describe the four types of structural isomerism exhibited by coordination compounds. (4)
Answer:
(i)

(ii) (1) Ionisation isomerism – Due to the difference of ions in aqueous solution.
eg. [Co(NH₃)₅Br]SO₄ and [C0(NH₃)₅SO₄]Br
(2) Linkage isomerism – Due to the difference in linking atoms.
[CO(NH₃)₅NO₂]Cl₂ and [Co(NH₃)₅(ONO)]Cl₂
(3) Hydrate isomerism – Due to the difference in no. of H₂O molecules inside and outside of the coordination sphere.
[Cr(H₂O)₆]Cl₃ and [Cr(H₂O)₅Cl]Cl₂.H₂O
(4) Coordination isomerism – Due to the exchange of ligands between the central meta-atoms.
[Co(NH₃)₆][Cr(CN)₆] and [Co(CN)₆][Cr(NH₃)₆]

Question 36.
(i) Write the products of the following reaction: (2)

(ii) Expalin Hell -Volhard-Zelinsky (HVZ) reaction. (2)
(iii) Suggest a suitable method for the following conversion. (2)

Answer:
(i)

(ii) HVZ reaction: Carboxylic acids containing α-hydrogen atoms are heated with halogen and red phosphorous to form an α-halogenated carboxylic acid.

(iii) Etards reaction: