Kerala Plus Two Chemistry Board Model Paper 2023 with Answers

Reviewing Kerala Syllabus Plus Two Chemistry Previous Year Question Papers and Answers Pdf Board Model Paper 2023 helps in understanding answer patterns.

Kerala Plus Two Chemistry Board Model Paper 2023 with Answers

Time: 2 Hours
Maximum: 60 Scores

Answer any 4 questions from 1 to 5. Each carries 1 score. (4 × 1 = 4)

Question 1.
Identify the order of the reaction if the unit of its rate constant is mol L^-1 s^-1.
Answer:
Zero Order

Question 2.
Zirconium and Hafnium have similar chemical properties. This is due to ______________
Answer:
Lanthanoid Contraction

Question 3.
Give an example for a polydentate ligand.
Answer:
EDTA

Question 4.
Which among the following compounds do not contain an alpha hydrogen?
(a) Propanone
(b) Ethanal
(c) Ethanol
(d) Benzaldehyde
Answer:
Benzaldehyde

Question 5.
A polyhalogen compound is ______________
(a) Chloroform
(b) Chlorobenzene
(c) Chloroethane
(d) Iodobenzene
Answer:
(a) Chloroform

Answer any 8 questions from 6 -15. Each carries 2 scores. (8 × 2 = 16)

Question 6.
(i) State RaouIt’s Law. (1)
(ii) Give an example for a solution which shows positive deviation from Raoult’s law. (1)
Answer:
(i) For a solution of volatile liquids, the partial vapour pressure of each component of the solution is directly proportional to its mole fraction present in solution.
\(\mathrm{P}_{\mathrm{A}}=\mathrm{P}_{\mathrm{A}}^0 \mathrm{X}_{\mathrm{A}}\)
(ii) Ethanol + Acetone

Question 7.
What are isotonic solutions? Give an example.
Answer:
Solutions with the same osmotic pressure are called isotonic solutions.
Eg. Blood and 0.9% normal saline solution

Question 8.
Write the anode reaction, cathode reaction, and net cell reaction of Daniel Cell.
Answer:
Daniel Cell
Anode: Zn → Zn²⁺ + 2e^–
Cathode: Cu²⁺+ 2e^– → Cu
Net Reaction: Zn + Cu²⁺ + 2e^– → Zn²⁺ + Cu
Zn + Cu²⁺ → Zn²⁺ + Cu

Question 9.
A first order reaction has a rate constant 1.15 × 10^-3 s^-1. How long will it take for 5 g of the reactant to decrease to 3g?
Answer:

Question 10.
Write the IUPAC name of the following coordination compounds.
(a) K3[Fe(CN)₆] (1)
(b) [Ni(CO)₄] (1)
Answer:
(a) Potassium Hexacyano Ferrate (III)
(b) Tetra Carbonyl Nickel (0)

Question 11.
Chloroform is stored in closed, dark coloured bottles filled up to the neck. Why?
Answer:
Chloroform reacts with oxygen to form a poisonous compound, phosgene (Carbonyl Chloride).

Question 12.
Phenols are acidic. Give reason.
Answer:
Acids are those substances which can release H⁺ easily. Phenol releases H⁺ easily and the phenoxide ion is more stabilised by resonance.

Question 13.
What is meant by diazotization reaction?
Answer:
Aniline on treatment with sodium nitrite and Con. HCl in ice-cold condition gives benzene diazonium chloride. This is known as diazotisation.

Question 14.
Most transition metals from coloured compounds. Why?
Answer:
Due to d-d transition.
The transition of d electron occurs between (n-1)d orbitals.

Question 15.
Write two differences between DNA and RNA.
Answer:

DNA	RNA
(i) Deoxyribonucleic acid.	(i) Ribonucleic acid.
(ii) Double helix structure.	(ii) Single helix structure.
(iii) Nitrogen bases A, T, C, G are present.	(iii) Nitrogen bases A, U, C, G are present.
(iv) Controls hereditary factors.	(iv) Controls synthesis of proteins.

Answer any 8 questions from 16-26. Each carries 3 scores. (8 × 3 = 24)

Question 16.
(i) Which of the following is a secondary cell? (1)
(a) Daniel cell
(b) Dry cell
(c) Lead storage battery
(ii) What is a fuel cell? (1)
(iii) Write the overall cell reaction of a H₂ – O₂ fuel cell. (1)
Answer:
(i) Lead storage battery.
(ii) Fuel cells are a galvanic cell that convert the energy of combustion of fuels into electrical energy.
Eg. H₂ – O₂ fuel cell
(iii) 2H₂ + O₂ → 2H₂O

Question 17.
The effect of temperature on the rate of a reaction is given by the Arrhenius equation.
(i) Write the Arrhenius equation. (1)
(ii) Define activation energy. (1)
(iii) Write the integrated rate expression for a zero order reaction. (1)
Answer:
(i) k = \(\mathrm{Ae}^{-\mathrm{Ea} / \mathrm{RT}}\)
where k is rate constant
A – Arrhenius factor
E_a – Energy of activation
R – Universal gas constant
T – Temperature.
(ii) The excess energy supplied to the reactant molecule to undergo chemical reaction is called activation energy.
(iii) k = \(\frac{\left[R_0\right]-[R]}{r}\)
k = rate constant
R₀ = initial concentration
R = final concentration
t = time

Question 18.
Hydrolysis of ester is a pseudo first order reaction.
(i) What do you mean by a pseudo first order reaction? (1)
(ii) The moiecularity of the reaction 2NO + O₂ → 2NO₂ is ______________ (1)
(iii) The rate expression for a reaction is k = [A]² [B]^1/2. Find the order of the reaction. (1)
Answer:
(i) Reactions that appear to be of higher order but behave as first order reactions are called pseudo first order reactions.
(ii) 2 + 1 = 3
No. of molecules taking part in the reaction.
(iii) Order = 2 + \(\frac{1}{2}\) = 2\(\frac{1}{2}\) = \(\frac{5}{2}\)

Question 19.
(i) Mention the industrial preparation of KMnO₄ from MnO₂. (2)
(ii) Draw the structure of Dichromate ion. (1)
Answer:
(i) It is prepared by fusion of MnO₂ with KOH. K₂MnO₄ is produced first. This is then disproportionate in acidic solution to give KMnO₄ by electrolytic oxidation.

Question 20.
(i) Explain one difference between double salt and a coordination compound? (2)
(ii) What is the co-ordination number of nickel in [Ni(CN)₄]^2-? (1)
Answer:
(i) Double Salt: Dissociate into simple ions completely in aqueous solution. These salts exist in the solid state only.
Coordination Compound: Do not dissociate into simple ions. Exist in solid state as well as in solution.
(ii) 4

Question 21.
(i) Mention two reactions that show the acidic character of alcohols. (2)
(ii) Name the product obtained when phenol is treated with a mixture of concentrated HNO₃ and concentrated H₂SO₄. (1)
Answer:
(i) CH₃ – CH₂OH + Na → CH₃CH₂ONa
ethanol + metallic sodium → sodium ethoxide

Question 22.
Explain the hydroboration oxidation reaction of propene with the help of a chemical equation. (3)
Answer:
Hydroboration is Antimarkonikov’s addition of water.

Question 23.
Identify X, Y, Z in the following reactions:

Answer:

Question 24.
(i) How can you prepare Benzaldehyde by Etard reaction? (1½)
(ii) Identify the product obtained by the reaction between acetic acid and ethanol? What is the name of this reaction? (1½)
Answer:
(i) Etard’s Reaction: Toluene on reaction with chromyl chloride followed by hydrolysis gives benzaldehyde.

(ii) Esterification Reaction

Question 25.
(i) What is Hinsberg Reagent Chemically? (1)
(ii) What is it used for? Explain your answer. (2)
Answer:
(i) Benzene sulphonyl chloride
(ii) To distinguish primary, secondary and tertiary amines.
Primary Amine + Hinsberg reagent → Salt soluble in alkali
Secondary Amine + Hinsberg reagent → Salt insoluble in alkali
Tertiary Amine + Hinsberg reagent → No reaction

Question 26.
(i) Name a fat-soluble vitamin? Which disease is caused by its deficiency? (2)
(ii) Name the enzyme used for the conversion of sucrose to glucose and fructose. (1)
Answer:
(i) A
Xerophthalmia
(ii) Invertase

Answer any 4 questions from 27 to 31. Each carries 4 scores. (4 × 4 = 16)

Question 27.
Abnormal values are obtained for certain solutes during the determination of molecular mass by colligative property method.
(i) Mention two reasons for the abnormal molecular mass values. (1)
(ii) How can this abnormal molecular mass be corrected? Substantiate your answer. (2)
(iii) Write any one application of reverse osmosis. (1)
Answer:
(i) Dissociation or association of solute particles.
(ii) Applying Van’t Hoff factor (i) to colligative properties
\(\mathrm{i}=\frac{\text { observed colligative property }}{\text { normal colligative property }}\)

1. Relative lowering of vapour pressure \(\frac{\Delta \mathrm{p}}{\mathrm{p}^0 \mathrm{~A}}=\mathrm{i} \frac{\mathrm{n}_{\mathrm{B}}}{\mathrm{n}_{\mathrm{A}}}\)
2. Elevation in boiling point ΔT_b = i k_b.m
3. Depression in freezing point ΔT_f = ik_f.m
4. Osmotic pressure π = \(\mathrm{i} \frac{\mathrm{n}}{\mathrm{v}} \mathrm{RT}\)

(iii) Desalination of sea water.

Question 28.
(i) Define galvanic cell. (1)
(ii) Corrosion may be considered as an electrochemical process. Why? (2)
(iii) Mention two ways to prevent corrosion. (1)
Answer:
(i) A device which converts chemical energy to electrical energy is known as an electrochemical cell or galvanic cell.
(ii) Pure iron acts as anode
At anode
2Fe(s) → 2Fe²⁺ + 4e^–
Electrons produced move through the metal and go to the cathode (impure surface) and reduce O₂ in the presence of H⁺.
H⁺ ions are formed by the dissolution of CO₂ in moisture.
At cathode: 4H⁺ (aq) + O₂ (g) + 4e^– → 2H₂O (l)
Overall reaction is 2Fe (s) + O₂ (g) + 4H⁺ (aq) → 2Fe²⁺ (aq) + 2H₂O (l)
Ferrous ions so formed are oxidised by atmospheric oxygen to ferric ions.
2Fe²⁺ + 2H₂O + \(\frac{1}{2}\)O₂ → Fe₂O₃ + 4H⁺
Fe₂O₃ + xH₂O → Fe₂O₃.xH₂O rust hydrated ferric oxide
(iii) (1) Applying paint or grease
(2) Coating with another active metal.

Question 29.
(i) Draw the geometrical isomers of [Pt(NH₃)₂Cl₂] and label them as cis and trans. (2)
(ii) Explain homoleptic and heteroleptic complexes. (2)
Answer:
(i)

(ii) Homoleptic complexes: Complexes in which only one type of ligand is used.
Eg: [Co(NH₃)₆]³⁺
Heteroleptic Complexes: Complexes in which more than one type of ligand is used.
Eg: [Co(NH₃)₄Cl₂]⁺

Question 30.
(i) Explain the Friedel-Crafts alkylation reaction of chlorobenzene. Mention the major product in this reaction. (2)
(ii) Identify X and Y in the reaction given below. (1)

Answer:
(i)

Chlorobenzene on treatment with methyl chloride in presence of anhydrous AlCl₃ gives a mixture of P-chloro toluene and O-chlorotoluene.

Question 31.
Explain the following reactions.
(i) Cannizzaro’s reaction (1½)
(ii) Aldol condenstion (1½)
(iii) Which among CH₃COOH and CH₂ClCOOH is more acidic? (1)
Answer:
(i) Cannizzaro Reaction: Aldehydes which do not contain a hydrogen undergo self oxidation and reduction to form acid salt and alcohol in presence of concentrated alkali.


(ii) Aldol condensation: Aldehydes or ketones with α-H atom undergo condensation to form β-hydroxy aldehyde or aldol in presence of dilute alkali.

(iii) CH₂ClCOOH due to – I effect.