Kerala Plus Two Chemistry Board Model Paper 2019 with Answers

Reviewing Kerala Syllabus Plus Two Chemistry Previous Year Question Papers and Answers Pdf Board Model Paper 2019 helps in understanding answer patterns.

Kerala Plus Two Chemistry Board Model Paper 2019 with Answers

Time: 2 Hours
Maximum: 60 Scores

Questions from 1-7 carry one score each, answer all the questions. (7 × 1 = 7)

Question 1.
Which of the following is an example of an ideal solution?
(a) Phenol + Aniline
(b) Ethanol + Acetone
(c) Acetone + Chloroform
(d) Benzene + Toluene
Answer:
(d) Benzene + Toluene

Question 2.
Identify the ore of zinc from the following:
(a) Siderite
(b) Malachite
(c) Haematite
(d) Calamine
Answer:
(d) Calamine

Question 3.
Write the ‘Spin-only’ formula used to calculate the magnetic moment.
Answer:
\(\mu=\sqrt{n(n+2)}\)
n = no. of unpaired electrons.

Question 4.
Give one example for a hexadentate ligand.
Answer:
EDTA

Question 5.
What is the chemical name of aspirin?
Answer:
Acetyl Salicylic Acid

Question 6.
Which synthetic zeolite is used for converting alcohol to gasoline?
Answer:
ZSM-5

Question 7.
What are the main constituents of Dettol?
Answer:
Chloroxylenol and Terpinol

Questions 8-20 carry two points each. Answer any ten questions. (10 × 2 = 20)

Question 8.
Write any two differences between crystalline and amorphous solids.
Answer:

Cystalline Substances	Amorphous Substances
1. Definite shape.	1. Irregular shape.
2. Sharp melting point.	2. Melting point is in a range.
3. Long range order.	3. Short range order.
4. Anisotropic.	4. Isotropic.

Question 9.
A compound with cubic structure is made of elements X and Y. X atoms are at the corners of the cube and Y atoms are at the body centre. Write the simplest formula of the compound.
Answer:
No. of X atoms (corners) = \(\frac{1}{8}\) × 8 = 1
No. of Y atoms (body centre) = 1
X : Y = 1 : 1 i.e. XY

Question 10.
When a zinc electrode (Zn (s)/Zn²⁺ (1m)) combines with SHE at 298 K and forms a galvanic cell. \(E_{\text {cell }}^0\) is found to be, 0.76 V. Write cell representation of the cell and calculate the standard electrode potential of the zinc electrode.
Answer:
When combined with SHE, the zinc electrode acts as an oxidation half cell (anode), while SHE acts as a reduction half cell or cathode.
\(E_{\text {cell }}^0\) = 0 – 0.76 = -0.76V

Question 11.
How many coulombs of electricity are required to produce 40 g of Al from Al3+ solution?
Answer:
Al³⁺ + 3e^– → Al
3 Faraday is needed to deposit 27g aluminum.
3F → 27 g Al
\(\frac{3F}{27}\) → 1 g Al
\(\frac{3F}{27}\) × 40 → 40 g Al
(\(\frac{3}{27}\) × 40) Faraday → 40 g Al
4.44 F → 40 g Al

Question 12.
What is chemical kinetics? Give any importance to it?
Answer:
Chemical kinetics is the branch of chemistry that deals with the rate of chemical reaction, factors affecting the rate, and the mechanism of a reaction.
Applications:

• To find how fast a medicine works.
• Speed of a reaction.
• Formation of ozone layer.

Question 13.
Explain homogeneous catalysis with one example.
Answer:
The catalysis in which both the reactants and the catalyst are in the same phase is called homogeneous catalysis.

Question 14.
Explain Mond Process.
Answer:
Mond Process: In this process, nickel is heated in a stream of carbon monoxide forming a volatile complex, nickel tetracarbonyl.
It is then decomposed to Ni and CO by heating at very high temperature.

Question 15.
PH₃ has a lower boiling point than NH₃, why?
Answer:
Due to the presence of strong hydrogen bonds, NH₃ has a high boiling point. But in PH₃ no hydrogen bond is present so its boiling point is low.

Question 16.
Silver atom has filled ‘d’ orbitals (4d¹⁰) in its ground state. Why is it considered a transition metal?
Answer:
Because its +1 and +2 oxidation state has incomplete d subshell. So it is a transition element.

Question 17.
Actinoid contraction is greater than Lanthanoid contraction. Account for it?
Answer:
The 5f electrons of actinoids are more effectively shielded from nuclear Charge than the 4f in lanthanoids.

Question 18.
Draw the cis and trans isomers of [CoCl₂(en₂]⁺?
Answer:

Question 19.
What is ‘DIBAL-H’? Give the importance of it?
Answer:
Diisobutylaluminium hydride (DIBAL – H) is a reducing agent.
Use: It can selectively reduce CN group or ester group without affecting double or triple bond.

Question 20.
Write the correct order of basic character of the following amines is (a) Gas phase and (b) in aqueous solution.
Answer:
In gas phase basicity is in the order 3° > 2° > 1°
(CH₃)₃N > (CH₃)₂NH > CH₃NH₂
In aqueous solution basicity is in the order 2° > 1 ° > 3°
(CH₃)₂NH > CH₃NH₂ > (CH₃)₃N

Questions from 21-29 carry three points each. Answer any seven questions. (7 × 3 = 21)

Question 21.
Write any three applications of Henry’s law.
Answer:

• Formation of bends as the scuba divers reach the Surface of the sea.
• Anoxia: At high altitudes, the amount of oxygen in the air is low, which creates a headache and is known as Anoxia.
• To increase the solubility of CO₂ in water, soda water is kept under high pressure in sealed vessels.

Question 22.
Activity and selectivity are the two important terms used in catalysis. Explain these terms with suitable examples.
Answer:
Activity: Catalyst can increase the rate of a chemical reaction.

The reaction takes place only in the presence of platinum.
Selectivity: A catalyst can direct a chemical reaction to a particular product.

Question 23.
(a) Write the formula for the following coordination compounds.
(i) Tetra ammine aquachlorido cobalt (III) chloride
(ii) Potassium tetrahydroxidozincate (II)
(b) Write the IUPAC names of the given coordination compound K[Co(SCN)₄]
Answer:
(a) [CO(NH₃)₄(H₂O)Cl]Cl₂
(b) K₂[Zn(OH)₄]
(c) Potassium Thiocyantatocobaltate (II)

Question 24.
Explain the S_N1 mechanism with a suitable example.
Answer:
Step I: Formation of a carbocation

Step II: Attack of a nucleophile

Question 25.
Complete the following.

Answer:

Question 26.
Write any three methods for the preparation of ethanamine (C₂H₅-NH₂).
Answer:
1. Reduction of nitriles

2. Reduction of Amides

3. Hoffmann bromamide reaction.
CH₃CH₂CONH₂ + Br₂ + NaOH → CH₃CH₂NH₂ + Na₂CO₃ + 2H₂O + 2NaBr

Question 27.
Write the important structural and functional differences between DNA and RNA.
Answer:

DNA	RNA
Double stranded.	Single stranded.
Nucleic acid present is deoxyribose.	Nucleic acid present is deoxyribose.
Bases present are adenine, Thymine, cytosine, guanine.	Bases present are Adenine, Uracil Cytosine and guanine.

Question 28.
(a) Name two synthetic polypeptide fibres.
(b) Indicate the monomers in each.
Answer:
(a) Nylon 6,6 – monomers – hexamethylenediamine and adipic acid
(b) Nylon 6 – caprolactum

Question 29.
Explain the therapeutic action of the following:
(a) Antacids
(b) Analgesics
(c) Antibiotics
Answer:
(a) Antacid: Used to reduce acidity in the stomach.
(b) Analgesic: to reduce pain or painkillers.
(c) Antibiotics: are drugs which kill or prevent the growth of microorganisms which are prepared from other microorganisms.

Questions 30-33 carry fourscore each. Answer any three questions. (3 × 4 = 12)

Question 30.
(a) Explain pseudo first order reaction with an example.
(b) A first order reaction has a rate constant 1.15 × 10^-3 S^-1. How long will 5g of this reactant take to reduce to 3g?
Answer:
(a) Reactions which appear to be higher order but follow first order kinetics are called pseudo first order reactions.
eg: CH₃COOC₂H₅ + H₂O → CH₃COOH + C₂H₅OH

Question 31.
(a) Why does ozone act as a powerful oxidising agent?
(b) How is O₃ estimated quantitatively?
Answer:
(a) Because ozone on decomposition gives nascent oxygen, which is a powerful oxidizing agent.
O₃ → O₂ + [O]
(b) When ozone and potassium iodide react, iodine is liberated. Now this iodide is titrated against a standard solution of sodium thiosulphate using starch as indicator.
2I + H₂O + O₃ → 2OH + I₂ + O₂
2Na₂S₂O₃ + I₂ → Na₂S₄O₆ + 2NaCl

Question 32.
(a) Explain the reason for the less reactivity of chlorobenzene than alkyl chloride?
(b) Identify the major product formed by the reaction of 2-bromobutane with alcoholic KOH. Give reason for it.
Answer:
(a) 1. Due to resonance effect, chlorobenzene develops a partial double bond character to the C-Cl bond which is difficult to break.
2. Instability of phenyl cation
3. Greater S character in sp² hybridised c-atom, which is more electronegative. Thus the bond in chlorobenzene becomes shorter and difficult to break.
4. Electron rich benzene ring

According to Saytzeft rule, more symmetric products are favoured.

Question 33.
Explain the following reactions.
(a) Aldol condensation
(b) HVZ reaction
Answer:
(a) Aldehydes or ketones with α hydrogen atom undergo condensation in the presence of dil. alkali to form aldols. (β hydroxy aldehyde). This reaction is known as aldol condensation.

(b) HVZ Reaction
Carboxylic acid with α hydrogen is heated with chlorine or bromine in the presence of red phosphorous to give α halo carboxylic acid.