Kerala Plus One Chemistry Board Model Paper 2020 with Answers

Reviewing Kerala Syllabus Plus One Chemistry Previous Year Question Papers and Answers Pdf Model 2020 helps in understanding answer patterns.

Kerala Plus One Chemistry Board Model Paper 2020

PART A

Answer any 7 questions from 1 to 9. Each carries 1 score. (7 × 1 = 7)

Question 1.
In hydrogen spectrum, the series of lines appearing in Ultra violet region are called ……….
(a) Balmer line
(b) Lyman line
(c) Pfund line
(d) Bracket line
Answer:
(b) Lyman series

Question 2.
Conjugate base of a strong acid is
(a) a weak base
(b) a strong base
(c) neutral
(d) a weak acid
Answer:
(a) a weak base

Question 3.
Which of the elements show least value of ionization energies in each periods?
(a) Alkaline earth metals
(b) Alkali metals
(c) Noble Gases
(d) Halogens
Answer:
(b) Alkali metals

Question 4.
Which Graph does not represent Boyle’s law?

Answer:

Question 5.
Which one of the following is a common component of photochemical smog?
(a) O₃
(b) CO
(c) CO₂
(d) CH₂
Answer:
(a) O₃

Question 6.
Boric acid is polymeric due to
(a) Its acidic nature
(b) The presence of H bond
(c) Its monobasic nature
(d) Geometry
Answer:
(b) The presence of H bond

Question 7.
In ………… reaction an element in one oxidation state is simultaneously oxidized and reduced.
Answer:
Disproportionation reaction

Question 8.
Delocalization of electrons involving a bond is known as …………..
Answer:
Hyperconjugation

Question 9.
The hydrocarbon which give benzene when pass¬ing through a red hot iron tube is
Answer:
Ethyne or acetylene

PART B

Answer any 10 questions from 10-22. Each carries 2 scores. (10 × 2 = 20)

Question 10.
Development of periodic table have made the study of elements and their compounds easier.
Answer:
1. The physical and chemical properties of the elements are periodic functiond of their atomic numbers.
2. Ununquadium

Question 11.
Irrespective of the source, pure sample of CO₂ always yields 27.27% mass of carbon and 72.72% mass of oxygen.
(a) Which law is illustrated here? (1)
(b) State the law. (1)
Answer:
(a) Law of Definite proportion
(b)The same compound always contains same elements in definite proportion by mass.

Question 12.
Give reason for the following:
(a) The first ionization enthalpy of oxygen is smaller compared to nitrogen. (1)

Answer:
(a) Electronic configuration of N – 1s² 2s² 2p³
Completely half filled orbitals are extra stable. So more energy is needed to remove the valence electron. IE is high.
Electronic configuration of O – 1s² 2s² 2p⁴

(b) Electron gain enthalpy of F is less than that of Cl. (1)
Answer:
In the case of F the electron to be added is to 2p orbital. 2p orbital is small and occurs repulsion. In Cl atom the electron to be added is to 3p orbital. 3p is larger than 2p and repulsion is less. So Cl is with more electron affinity than Flourine.

Question 13.
Density of a gas at 27°C and 1 atm is 256 g/L. Calculate its molar mass [IR = 0.081 L atm mol^-1 k^-1]. (2)
Answer:
M = \(\frac{dRT}{P}\). P = 1 atm, R = 0.0821, T = 27°C = 300k
d = 256 g/L
= \(\frac{256 \times 0.0821 \times 300}{1}\) = 6305.28 g

Question 14.
Classify the following properties into extensive and intensive.
(Density, Enthalpy, Specific heat capacity, Entropy)
Answer:
Tablee

Question 15.
(a) The water solutions of the ionic compounds KCl, CH₃COOK and NH₄Cl show different pH value.
Identify the acidic, basic and neutral solution among these. (1)
Answer:
KCl gives neutral solution with pH = 7 because it is formed from strong base KOH and strong acid HCl.
CH₃COOK – basic pH > 7. Because it is formed from strong base KOH and weak acid CH₃COOH.
NH₄Cl → acidic pH < 7 because it is formed from weak base NH₄OH and strong acid HCl.

(b) What is ionic product of water? (1)
Answer:
Ionic product of water Kw for the reaction is

It is the product of the molar concentration of H+ and OH’ ions in water.

Question 16.
H₂O₂ is an important chemical.
(a) Give a method to prepare H₂O₂. (1)
(b) Represent the structure of H₂O₂. (1)
Answer:

Question 17.
Litium shows a diagonal relationship with magnesium.
Give any two similarity between Li and Mg. (2)
Answer:
1. They are hard
2. They do not form super oxides.

Question 18.
Calculate the wave number radiation due to transition of an electron from 4th to 2nd orbit.
(R_H = 109677 cm^-1).
Answer:

Question 19.
Draw the Newman’s projection of the clipsed and staggered conformation of ethane.
Answer:

Question 20.
Diborane is an electron deficient compound.
(a) Name the special bonds that present in diborane.
(b) How will you convert diborane into inorganic benzene?
Answer:
a. Banana bond or 3 centred – 2e bond
b. By reacting Ammonia with diborane inorganic benzene is formed.
3B₂H₆ + 6NH₃ → 2B₃N₃H₆ + 12H₂

Question 21.
What happen when
(a) Borax is heated strongly. (1)
Answer:
(a) Sodium meta borate and Boric anhydride is formed.

Or
On heating Borax first loses water molecules and swells up. On further heating it.turns into a transparent liquid which solidifies into glass like material known as borax bead.

(b) Boric acid is added to water. (1)
Answer:
When boric acid is added to water it act as Lewis acid by accepting electrons from a hydroxyl ion. B(OH)3 + 2HOH [B(OH)4]’ + H30+

Question 22.
Give the structure of the following compound:
(a) 4-Chloro-2-Methyl Pentane (1)
(b) 4-hydroxy pentan – 1- oic acid. (1)
Answer:

Answer any 7 questions from 23-31. Each carries 3 scores. (7 x 3 = 21)

Question 23.
(a)What is atomic mass unit (amu)? (1)
Answer:
1 amu = 1/12 th of a mass of a C-12 atom.

(b)KClO₃ on heating decomposes to KCl and O₂. Calculate the mass of O₂ produced by heating 50 gm KClO₃.
(Hint. 2KClO₃ → 2KCl + 3O₂)
Answer:
2KClO₃ → 2KCl + 3O₂
2 × 122.5g → 2 × 74.55 + 3 ×32
245.g KClO₃ → 96g O₂
1g KClO₃ → \(\frac{96}{245}\) g O₂
50g KClO₃ → × 50 = 19.58g

Question 24.
(a) Classify the following molecule according to the type of hydrogen bond H₂O, O-nitrophenol.
Answer:
Water – Inter molecular H – Bonding.
O – nitro phenol – Inter molecular H – bonding.

(b) NF₃ and NH₃ show dipole moment. But the dipole moment of NF₃ is less than that of NH₃. Why? (2)
Answer:

The orbital dipole due to lone pair is in the opposite direction with the resultant dipole moment of the N-F bonds.
So dipole moment is less.

The orbital dipole due to lone pair is in the same direction with the resultant dipole moment of the N- H bonds.
So net dipole moment is more.

Question 25.
(a) Give Vander Waal’s equation for ‘n’ mole of a gas. (1)
Answer:
(P – \(\frac{n^2 a}{v^2}\))(v – nb) = nRT
P – Pressure
a, b – vanderWaals constant
n – no. of moles
v – volume
T – temperature
R – Universal gas constant

(b) Write four postulates of kinetic theory of gases. (2)
Answer:
1. Gases consists of large no. of minute particles called molecules.
2. Particles are always in constant random motion.
3. During their motion they collide with each other and also with the walls of the container. These collisions results pressure.
4. Collisions of gas molecules are perfectly elastic.

Question 26.
(a) Give the criteria for spontaneity of a process in terms of free energy change (∆G). (1)
(b) How it is related to the enthalpy and entropy of a system? (1)
(c) What happens to the entropy during the following changes?
(i) A liquid crystallises into a solid.

Answer:
(a) For a spontaneous process ∆G should be -ve.
(b) ∆G = ∆H – T∆S
(c) 1. ∆S = -ve i.e. decreases
2. ∆S = +ve i.e. increases

Question 27.
(a) Using stock notation represent the following compounds:
(i) SnO₂
(ii) Cr₂O₃ (1)
Answer:
(i) Sn(IV)O₂
(ii) Cr₂(III)O₃

(b) In the reaction
2Cu₂O(S) + 2CU₂S(S) → 2CU(S) + SO₂
(i) Subtance oxidized
(ii) Subtance reduced
(iii) Oxidising agent
(iv)Reducing agent (2)
Answer:
(i) S is oxidised
(ii) Cu is reduced
(iii) Cu₂O oxidising agent
(iv) Cu₂S reducing agent

Question 28.
(a) Write the name of any one salt responsible for the permanent hardness of water. (1)
Answer:
(a) MgCl₂ or CaCl₂ or CaSO₄ or MgSO₄

(b) Explain one chemical method for removing per-manent hardness of water. (1)
Answer:
(1) Calgons process
Hard water is allowed to pass through Calgon. i.e. Sodium hexametaphosphate (Na6P6018) (2) Add washing soda to hard water.

(c) Suggest a disadvantages of hard water. (1)
Answer:
Soap do not lather in hard water.
Scales are formed in the boilers.

Question 29.
(a) What is plaster of paris? (1)
(b) Write the chemical equation showing the preparation of plaster of paris from Gypsum. (1)
(c) What is dead burnt plaster? (1)
Answer:
(a) CaSO₄.1/2 H₂O

Question 30.
(a)Consider the reaction given below:

(i) Identify the product X.
(ii) Name the reaction.
Answer:

(i) X= 1-Bromopropane
(ii) Anti markonikov’s addition
or
Peroxide effect
or
Kharash effect

(b) Complete the following reaction:

Answer:
CaC₄ + 2H₂0 → C₂H₂ + Ca(OH)₂