Kerala Plus Two Chemistry Question Paper March 2023 with Answers

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

Kerala Plus Two Chemistry Previous Year Question Paper March 2023

Time: 2 Hours
Total Scores: 60

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

Question 1.
The unit of rate constant of a zero-order chemical reaction is _______________
Answer:
mol L^-1 s^-1

Question 2.
Among the following transition elements which one has a filled d orbital?
(a) Ag
(b) Ti
(c) Mo
(d) Ni
Answer:
(a) Ag

Question 3.
Give an example of a didentate ligand.
Answer:
Ethylene diamine (en), oxalate ion (\(\mathrm{C}_2 \mathrm{O}_4^{2-}\))

Question 4.

The name of this reaction is _______________
Answer:
Finkelstein Reaction

Question 5.
Identify the product ‘X’ in the chemical reaction given below:

Answer:
C₆H₅CHO benzaldehyde

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

Question 6.
State Henry’s law. Write any one application of it.
Answer:
Henry’s Law: The solubility of a gas in a liquid is directly proportional to the pressure applied to it.
p = K_H.x
p = pressure
x = mole fraction of gas
Application:
When the soda bottle opens a fizz sound is produced. Anoxia and bends are also examples.

Question 7.
What are Ideal Solutions? Give one example.
Answer:
Ideal solutions are solutions which obey Raoults law.
P_A = \(\mathrm{P}_{\mathrm{A}}^0 \cdot x_{\mathrm{A}}\), ΔV_mix = 0, ΔH_mix = 0
Eg. n-hexane and n-heptane

Question 8.
\(\wedge_{\mathrm{m}}^0\) for NaCl, HCl and CH₃COONa are 126.4, 425.9 and 91.0 s cm² mol^-1 respectively. Calculate \(\wedge_{\mathrm{m}}^0\) for CH₃COOH.
Answer:
\(\lambda_{\mathrm{m}}^0\)CH₃COOH = \(\lambda_{\mathrm{m}}^0\)CH₃COONa + \(\lambda_{\mathrm{m}}^0\)HCl – \(\lambda_{\mathrm{m}}^0\)NaCl
= 91 + 425.9 – 126.4
= 390.5 S cm² mol^-1

Question 9.
(i) What are Pseudo first-order reactions? (1)
(ii) Write one example for a pseudo-first-order reaction. (1)
Answer:
(i) These are reactions that appear to follow a higher order but follow the first order.
(ii) Hydrolysis of ester

Question 10.
(i) Transition elements show variable oxidation state. Why? (1)
(ii) Identify the element in the 3d transition metal series that exhibits the maximum number of oxidation states. (1)
Answer:
(i) Because there is not much difference in the energy levels of 3d and 4s electrons, or there are partially filled (n-1)d orbital.
(ii) Manganese (Mn)

Question 11.
Write the IUPAC names of the following compounds:
(a) [Co(NH₃)₄(H₂O)Br]Br₂
(b) K₃[Al(C₂O₄)₃]
Answer:
(a) Tetraammineaquabromidocobalt (III) bromide
(b) Potassium trioxalatoaluminate (III)

Question 12.
Differentiate between S_N1 and S_N2 reactions.
Answer:

SN1	SN2
1. Takes place in 2 steps.	1. Through a single step.
2. Carbocation intermediate is formed.	2. No intermediate is formed.
3. Racemisation occur.	3. Inversion of configuration occurs.

Question 13.
How is phenol manufactured industrially? Write the chemical equation.
Answer:
Cumene is oxidized in the presence of air and then hydrolyzed in the presence of acid to get phenol.

Question 14.
Aniline does not undergo Friedelcraft’s reaction. Why?
Answer:
Aniline forms a salt with anhydrous aluminium chloride which is used as a catalyst in Friedel crafts reaction. So the catalyst is not available for the reaction and hence it does not undergo Friedel Crafts reaction.

Question 15.
What are oligosaccharides? Give any two examples.
Answer:
Oligosaccharides are carbohydrates that give two to ten monosaccharide units on hydrolysis.
E.g. Sucrose, maltose.

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

Question 16.
(i) Define Molar Conductivity. (1)
(ii) Graphically represent the variation of molar conductivity with concentration for strong and weak electrolytes. (2)
Answer:
(i) Molar conductivity is the conductivity of 1 mole of an electrolytic solution kept between two electrodes of a conductivity cell with a unit area of cross section and at a distance of unit lengths.
(ii) λ_m = \(\frac{1000 \kappa}{m}\)

Question 17.
(i) A first-order reaction is found to have a rate constant, k = 6.8 × e 10^-14 s^-1. Find the half-life of the reaction. (1)
(ii) Write the integrated rate equation for a first-order reaction and explain the terms in it. (2)
Answer:

k – dissociation constant or rate constant
t – time
R₀ – initial concentration
R – final concentraton

Question 18.
Explain the effect of temperature and catalyst on the rate of chemical reaction.
Answer:
For every 10° rise in temperature rate constant doubles. Because with temperature rise, the number of molecules with energy equal to or greater than activation energy increases, and therefore rate constant also increases.
A catalyst increases or decreases the rate of a reaction by providing an alternate path for the reaction with low activation energy.

Question 19.
Write the preparation of K₂Cr₂O₇ from Chromite ore.
Answer:
1. Conversion of chromite ore to sodium chromate by fusing with sodium carbonate in the presence of air.
4FeCr₂O₄ + 8Na₂CO₃ + 7O₂ → 8Na₂CrO₄ + 2Fe₂O₃ + 8CO₂
2. Sodium chromate is acidified with sulphuric acid to form sodium dichromate.
2Na₂CrO₄ + 2H⁺ → Na₂Cr₂O₇ + 2Na⁺ + H₂O
3. Conversion of sodium dichromate to potassium dichromate by treating with potassium chloride.
Na₂Cr₂O₇ + 2KCl → K₂Cr₂O₇ + 2NaCl

Question 20.
(i) What is a Spectrochemical series? (1)
(ii) Draw a figure to show the splitting of d orbitals in an octahedral crystal field and label the diagram. (2)
Answer:
(i) It is a series in which the ligands are arranged in the increasing order of their field strength.
(ii)

Question 21.
Name the products formed when phenol is treated with the following reagents:
(i) Bromine water (1)
(ii) Zinc dust (1)
(iii) Conc. HNO₃ (1)
Answer:

Question 22.
Explain the following:
(i) Kolbe’s reaction (1½)
(ii) Reimer-Tiemann reaction (1½)
Answer:
(i) Kolbe’s Reaction: Sodium phenoxide reacts with CO₂ at 400 K and 4-7 atm sodium salt of salicylic acid is formed. This on acidification gives salicylic acid.

(ii) Reimer-Tiemann Reaction: Phenol reacts with chloroform in the presence of NaOH followed by acidification we get salicylaldehyde.

Question 23.
(i) Write any two nucleophilic addition reactions of aldehyde. (2)
(ii) Name the product formed when ethanal is reduced with LiAlH₄. (1)
Answer:

(ii) Ethanol OR, Ethyl alcohol (C₂H₅-OH OR, CH₃-CH₂-OH)

Question 24.
(i) Which one is more reactive among aldehydes and ketones? (1)
(ii) Describe any two tests to distinguish aldehydes from ketones. (2)
Answer:
(i) Aldehydes
(ii)

	Aldehyde	Ketone
Tollens Test	Gives silver mirror	No silver mirror is obtained
Fehling’s Test	The red precipitate of cuprous oxide	No red ppt.

Question 25.
(i) What is the Carbylamine reaction? (1)
(ii) Explain why aniline is less basic than ammonia. (2)
Answer:
(i) Primary amine reacts with chloroform in the presence of KOH to form isocyanides.
RNH₂ + CHCl₃ → RNC Carbylamine
(ii) In aniline the lone pair electron of N is in conjugation with the benzene ring. So it is not available for protonation. So it is less basic than NH₃.

Question 26.
(i) What are essential and non-essential amino acids? (1)
(ii) Explain the amphoteric behavior of amino acids. (2)
Answer:
(i) The amino acids which can be synthesized in the body are known as non-essential amino acids.
eg. Glycine, Alanine
The amino acid that cannot be synthesized in the body and get through diet is known as essential amino acid.
eg. Valine, Leucine

(ii) The same compound contains both +ve and -ve charges and hence shows an amphoteric nature.

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

Question 27.
(i) What are Colligative properties? (1)
(ii) Write any two colligative properties. (1)
(iii) What is reverse osmosis? Mention one important practical utility of reverse osmosis. (2)
Answer:
(i) Properties that depend only on several particles.
(ii) 1. Relative lowering of vapour pressure
2. Depression at the freezing point
3. Elevation in boiling point
4. Osmosis
(ii) If a pressure higher than the osmotic pressure is applied to the solution side, the direction of osmosis gets reversed. This phenomenon is called reverse osmosis.
The application of reverse osmosis is the desalination of seawater.

Question 28.
Lead storage battery which is commonly used in automobiles is an example of a secondary cell.
(i) Write the name of the anode and cathode used in this cell. (1)
(ii) Write the reactions taking place in the anode and cathode of this cell. (2)
(iii) Explain how this cell can be recharged. (1)
Answer:
(i) Anode: Lead (Pb)
Cathode: A grid of lead packed with PbO₂
(ii) Anode reaction:
Pb + \(\mathrm{SO}_4^{2-}\) → PbSO₄ + 2e^–
Cathode reaction:
PbO₂ + \(\mathrm{SO}_4^{2-}\) + 4H⁺ + 2e^– → PbSO₄ + 2H₂O
(iii) The cell can be recharged by applying an external potential higher than the potential of the cell.

Question 29.
(i) Drew the structure of the geometrical isomers of the coordination compound [Co(NH₃)₄Cl₂]. (2)
(ii) Based on Valence Bond Theory (VBT) explain the structure and magnetic property of [Ni(CN)₄]^2-. (2)
Answer:
(i)

(ii) In [Ni(CN)₄]^2-, Ni in dsp² hybridisation. Square planar geometry.
Due to the absence of unpaired electrons, the complex is diamagnetic.

Question 30.
(i) Identify the major and minor products obtained by the reaction between 2-bromo butane and alcoholic KOH. (2)
(ii) Name and state the rule behind the formation of these products. (2)
Answer:
(i) Major product is But-2-ene (CH₃ – CH = CH – CH₃)
Minor product is But-1-ene (CH₃ – CH₂ – CH = CH₂)
(ii) Saytzeff’s rule: It states that in dehydrohalogenation reactions, the major product is alkene which contains a maximum number of alkyl groups around the C = C bond.

Question 31.
(i) Explain the Haloform reaction. (2)
(ii) How will you prepare benzaldehyde by the Gatterman-Koch reaction? (1)
(iii) Write the name of the reaction involved in the following conversion:

Answer:
(i) Haloform Reaction: Compounds with CH₃-CO or CH₃-CHOH-group, when treated with sodium hypohalite we get haloform (CHX₃).
R – CO – CH₃ → R – COONa + CHX₃
(ii) Benzene when treated with CO and HCl in the presence of anhydrous aluminium chloride or cuprous chloride we get benzaldehyde.

(iii) Clemmensen Reduction.