Kerala Plus Two Chemistry Question Paper SAY 2019 with Answers

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

Kerala Plus Two Chemistry Previous Year Question Paper SAY 2019

Time: 2 Hours
Total Scores: 60

Questions Number 1-7 carry 1 Score each. Answer all the questions. (7 × 1 = 7)

Question 1.
The smallest repeating structural unit of a crystal is called
(a) Lattice point
(b) Bravais lattice
(c) Space lattice
(d) Unit cell
Answer:
(d) Unit cell

Question 2.
Which of the following is not a colligative property?
(a) Osmotic pressure
(b) Vapour pressure
(c) Elevation of boiling point
(d) Depression of freezing point
Answer:
(b) Vapour Pressure

Question 3.
The ion that is more effective for the coagulation of negatively charged As₂S₃ sol is
(a) Al³⁺
(b) \(\mathrm{PO}_4^{3-}\)
(c) \(\mathrm{SO}_4^{2-}\)
(d) Na⁺
Answer:
(a) Al³⁺

Question 4.
The role of NaCN in Froth flotation process involving an ore containing ZnS and PbS is as a ______________
Answer:
Depressant

Question 5.
The crystal field splitting energy for Octahedral (Δ₀) and Tetrahedral (Δ_t) complexes are related as
(a) Δ_t = \(\frac{3}{5}\) Δ₀
(b) Δ_t = \(\frac{5}{3}\) Δ₀
(c) Δ_t = \(\frac{4}{9}\) Δ₀
(d) Δ_t = \(\frac{9}{4}\) Δ₀
Answer:
(c) Δ_t = \(\frac{4}{9}\) Δ₀

Question 6.
The monomer of natural rubber is ______________
Answer:
Isoprene

Question 7.
Give an example for a Non-narcotic analgesic.
Answer:
Aspirin or Paracetamol

Questions number 8-20 carry 2 Scores each. Answer any 10 questions. (10 × 2 = 20)

Question 8.
In terms of band theory, what is the difference between a conductor and a semiconductor?
Answer:
In conductor, the valence band is partially filled and it overlaps with a high energy unoccupied conduction band. Electrons can easily flow under an applied electric field.
In semiconductors, the valence band is filled and there is a small gap between the valence band and the next higher conduction band. Some electrons can jump from the valence band to the conduction band and conduct electricity.
OR

In a conductor, the energy gap between the valence band & conduction band is very small, but in a semiconductor there is always a small energy gap between them.

Question 9.
How do galvanic cells differ from electrolytic cells?
Answer:
Galvanic cell: A device that converts chemical energy to electrical energy is known as an electrochemical cell or galvanic cell.
eg. Daniel cell.
Electrolytic cell: A device that converts electrical energy into chemical energy is known as an electrolytic cell.
eg. dry cell, lead storage cell.

Question 10.
Differentiate molecularity and order of a reaction.
Answer:

Order	Molecularity
1. It is the sum of the powers of the concentration terms in the rate law.	1. It is the no. of reacting molecules or atoms, or ions which collide simultaneously to bring about the reaction.
2. Experimentally determined.	2. Theoretical concept.
3. It can have whole no. fractional or zero values.	3. It can have only whole numbers. values other than zero.
4. Gives an idea about Mechanism.	4. No idea about mechanism.

Question 11.
Write the Arrhenius equation and identify the terms in it.
Answer:
K = \(A e^{-E a / R T}\)
or
log K = log A – \(\frac{E a}{R T}\)
or
\(\log \frac{K_2}{K_1}=\frac{E_a}{2.303 R}\left(\frac{1}{T_1}-\frac{1}{T_2}\right)\)
K – Rate constant
A – Arrhenius constant
E_a – Energy of Activation
T – Temperature
R – Universal Gas Constant
K₁ – Rate constant at temperature T₁
K₂ – Rate constant at temperature T₂

Question 12.
Write any two differences of physical absorption and chemical adsorption?
Answer:

Physisorption	Chemisorption
1. Due to Vander Waal’s forces.	1. Due to chemical bond formation.
2. Low temperature is favoured.	2. High temperature is favoured.
3. Not specific.	3. Highly specific.
4. Reversible.	4. Irreversible.

Question 13.
Match the following:

A	B
(i) Zinc	(a) Bauxite
(ii) Iron	(b) Malachite
(iii) Copper	(c) Calamine
(iv) Aluminum	(d) Magnetite
	(e) Galena

Answer:
Zinc – Calamine
Iron – Magnetite
Copper – Malachite
Aluminium – Bauxite

Question 14.
Write the main differences between the properties of white phosphorous and red phosphorous.
Answer:

White Phosphorous	Red Phosphorous
1. White waxy solid, poisonous.	1. Iron grey luster, non-poisonous, odourless.
2. Insoluble in water but soluble in CS2.	2. Insoluble in water and CS2.
3. Glows in dark.	3. Does not glow in the dark.
4. Less reactive.	4. More reactive.

Question 15.
Which element of the 3d series exhibits the largest number of oxidation states? Why?
Answer:
Manganese
Due to the completely half-filled electronic configuration. So it shows an oxidation state from +2 to +7.

Question 16.
What is Lanthanoid contraction? Give reason for it.
Answer:
The steady decrease in the size of atoms or ions of the lanthanides with increase in atomic number is called lanthanoid contraction. Along the lanthanoid series the nuclear charge increases by one unit and the new electron is added to the same inner subshell, namely 4f. The electrons in f orbital cannot effectively screen the nucleus.

Question 17.
Write the IUPAC name of the following:
(i) [Ni(CO)₄]
(ii) K₃[Fe(CN)₆]
Answer:
(i) [Ni(CO)₄] – Tetracarbonyl Nickel (O)
(ii) K₃[Fe(CN)₆] – Potassiumhexacyanoferrate (III)

Question 18.
Write the preparation of propan-2-ol from a Grignard reagent.
Answer:

Question 19.
Phenols are acidic. Why?
Answer:
Phenol forms phenoxide ion which is more stable due to delocalisation.

Question 20.
What are homopolymers and co-polymers? Give one example for each.
Answer:
Homopolymer – contains the same monomer units.
eg. Polythene, Teflon, PVC
Copolymer – Contains two or more different monomer units.
eg. nylon 6, 6, Buna – S

Questions Number 21-29 carry 3 Scores each. Answer any 7 questions. (7 × 3 = 21)

Question 21.
Aluminium crystallizes in a ccp structure and its metallic radius is 125 pm. Calculate the edge length of the unit cell and also find the number of unit cells in 1 cm³ of Aluminium.
Answer:
a = 2√2r
= 2√2 × 125
= 353 pm
Volume of unit cell = a³
a³ = (353 × 10-10 cm)³ = 4.44 × 10^-23
No. of unit cell in 1 cm³ = \(\frac{1}{4.44 \times 10^{-23}}\)

Question 22.
What is meant by positive and negative deviation from Raoult’s law and how is the sign of ΔmixH related to positive and negative deviation?
Answer:

Question 23.
What is an adsorption isotherm? Describe Freundlich adsorption isotherm.
Answer:
A graph drawn between the amount of gas adsorbed per gram of the adsorbent x/m and the pressure of the gas at constant temperature is known as an adsorption isotherm.
Frendlich adsorption isotherm
\(\frac{x}{m}=k p^{1 / n}\)
k – constant
n – integers
x & m – masses of adsorbate and adsorbent
\(\log \frac{x}{m}=\log k+\frac{1}{n} \log p\)

Question 24.
Explain how nitric acid is manufactured by Ostwald’s process?
Answer:
Ostwald Process
I. Ammonia is mixed with oxygen and is passed over platinum gauze catalyst at 500 K and 9 bar pressure

II. Oxidation of NO to NO₂: NO combines with excess O2 to form NO2 when the temp is lowered.
2NO + O₂ \(\rightleftharpoons\) 2NO₂
III. NO₂ is dissolved in water to form nitric acid
3NO₂ + H₂O → 2HNO₃ + NO

Question 25.
Explain S_N1 mechanism with suitable examples.
Answer:
Reaction of ter-butylbromide with alkali (OH)
Step I: Formation of a carbocation

Step II: Addition of Nucleophile

Question 26.
Write the reaction of ethyl bromide with the following reagents:
(a) aq. KOH
(b) KCN
(c) AgCN
Answer:
(a) CH₃ – CH₂Br + aq.KOH → CH₃CH₂OH
(b) CH₃ – CH₂Br + KCN → CH₃CH₂CN
(c) CH₃ – CH₂Br + AgCN → CH₃CH₂NC

Question 27.
Explain the reaction between primary, secondary, and tertiary amines with Hinsberg’s reagent.
Answer:
1. A primary amine reacts with Heisenberg’s reagent to form alkyl benzene sulphonamide which is soluble in alkali.

2. A secondary amine reacts with Hinsberg reagent to form dialkyl benzene sulphonamide, which is insoluble in alkali

3. A tertiary amine does not react with Hinsberg reagent.

Question 28.
Write any three differences of RNA and DNA.
Answer:

RNA	DNA
1. Contains Ribonucleic acid.	1. Deoxy ribonucleic acid.
2. Single stranded α-helical structure.	2. Double stranded α-helical structure.
3. Less stable.	3. More stable.
4. Contains bases such as uracil, cytosine, adenine, and guanine.	4. Contains bases such as Thymine, Cytosine, Adenine, and guanine.
5. Controls synthesis of proteins.	5. Controls the hereditary effect.

Question 29.
Write the therapeutic action of the following drugs:
(a) Antacids
(b) Disinfectants
(c) Antibiotics
Answer:
(a) Antacid: Substances which remove excess acid in the stomach are known as antacids.
(b) Disinfectants: Disinfectants are chemicals which kill microorganisms but are not safe to be applied to living tissues.
(c) Antibiotics: Antibiotics are chemical substances which, in low concentration, destroy or inhibit the growth of microorganisms by intervening in their metabolic process.

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

Question 30.
(a) Describe the Standard Hydrogen Electrode (SHE). (3)
(b) The emf of the cell obtained by coupling an electrode with SHE was 1.37 V. If SHE is the +ve electrode, find the potential of the given electrode. (1)
Answer:
(a) Standard Hydrogen electrode (SHE)
It consists of a Pt wire sealed into a glass tube carrying a platinum foil at one end. The electrode is placed in an aqueous acid solution containing 1 M H⁺ ions, pure hydrogen gas at 1 bar pressure is bubbled through the solution at 298 K. The electrode potential of SHE is taken as zero.

Question 31.
Draw the geometrical isomers of [PtCl₂(en)₂]²⁺. Which of the isomers are optically active? Give reason. (4)
Answer:

Cis isomer is optically active because it is unsymmetric and it forms a non-superimposable mirror image.

Question 32.
(a) What is Cumene? Explain the preparation of phenol from Cumene. (3)
(b) Identify the compound A. (1)

Answer:
(a) Cumene is isopropylbenzene

Question 33.
Describe the following with equations:
(a) Etard reaction. (2)
(b) Aldol condensation. (2)
Answer:
(a) Toluene reacts with chromyl chloride in carbon disulphide to give benzaldehyde.

(b) Aldol condensation

Aldehydes containing α hydrogen atom undergo aldol condensation in the presence of dil alkali to form β-hydroxy aldehyde or aldol.