Kerala Plus One Chemistry Question Paper Sep 2021 with Answers

Reviewing Kerala Syllabus Plus One Chemistry Previous Year Question Papers and Answers Pdf Sep 2021 helps in understanding answer patterns.

Kerala Plus One Chemistry Question Paper Sep 2021

Time : 2 Hours
Maximum : 60 Scores

Answer any 6 questions from 1to12. Each carries 2 scores. (6 × 2 = 12)

Question 1.
Write the orbital representation for the following quantum numbers:
(a) n = 3,I = 1
(b) n = 5, I = 0
Answer:
(a) 3p
(b) 5s

Question 2.
Identify the correct electronic configuration of Cu (z = 29) from the following and give reason for your answer,
(a) Cu – 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹
(b) Cu – 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 3d⁹ 4s²
Answer:
(a) Cu – 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹

Question 3.
Fill in the blanks:

Molecule	Structure	Bond angle
BF3	………….	120°
BeCl2	Linear	…………..

Answer:

Molecule	Structure	Bond angle
BF3	Trigonal planar	120°
BeCl2	Linear	180°

Question 4.
Write any two postulates of Kinetic Molecular Theory of gases.
Answer:
1. Molecules are always in random motion.
2. During their motion they collide with each other and with the side of the container.

Question 5.
Write Hess’s law of constant heat summation.
Answer:
The total enthalpy change for a process is same whether it takes place in single step or several step.

Question 6.
Write expression for equilibrium constant (Kc) for the following reactions:

Answer:
(a) K_C = \(\frac{\left[\mathrm{NH}_3\right]^2}{\left[\mathrm{~N}_2\right]\left[\mathrm{H}_2\right]^3\)

(b) K_C = \(\frac{[\mathrm{HI}]^2}{\left[\mathrm{H}_2\right]\left[\mathrm{I}_2\right]}\)

Question 7.
What are buffer solutions? Give an example for buffer solution.
Answer:
Solutions which resist change in pH.
eg. Acidic buffer
CH₃COOH + CH₃COONa .
acetic acid + sodium acetate

Question 8.
(i) Write the chemical name of Baking Soda. (1)
Answer:
Sodium bicarbonate [NaHCO₃]

(ii) Name the product formed when Washing Soda is heated above 373 K. (1)
Answer:
Na₂CO₃ or Soda ash or Anhydrous sodium carbonate

Question 9.
Write the position isomers of an alcohol with molecular formula C₃H₈O.
Answer:
C₃H₈O

Question 10.
Write the complete structural formula and condensed structural formula of 2-Methyl pentane.
Answer:

Question 11.
Write A and B in the following reactions:

Answer:

Question 12.
Write the geometrical isomers of But-2-ene.
Answer:

Answer any 8 questions from 13 to 28. Each carries 3 scores. (8 × 3 = 24)

Question 13.
(i) WriteAvogadro number. (1)
Answer:
6.022 × 10²³

(ii) How many moles of water molecules are present in 180 g of water? (molecular mass of water = 18 g). (2)
Answer:
No. of moles = \(\frac{wt}{Mwt}\) = \(\frac{180}{18}\) = 10 moles

Question 14.
(i) Define Molarity. (1)
Answer:
No. of moles of solute particles dissolved in 1000 ml of solution.
M = \(\frac{n_B}{V}\) × 1000
n_B – no of moles of solute
V – vol. of solution in l

(ii) State law of multiple proportions. (2)
Answer:
It state that when two elements combine to form more than one compounds the different masses of one of the element combines with fixed mass of other bear a simple hole no ratio by mass.

Question 15.
Account for the following:
(a) Atomic radius increases from top to bottom in a group.
Answer:
As we move down the group new shells are added and the size is increased.

(b) Electron gain enthalpy of F is lower than that of Cl.
Answer:
It is because 2p orbital of F atom is smaller compared to 3p of Cl atom. In chlorine one more, electron can be added to 3p orbital with less repulsion.

Question 16.
(i) Depending upon the type of atomic orbital being filled with electrons, the elements are classified into four blocks. Name these four blocks of elements. (1)
Answer:
s block – last electron enters to s orbital
p block – last electron enters to p orbital
d block – last electron enters to d orbital
f block – last electron enters to f block orbital

(ii) State the modern periodic law of elements. (2)
Answer:
The physical and chemical properties of elements are periodic functions of their atomic numbers.

Question 17.
(i) What is bond order according to M.O. theory? (1)
Answer:
No. of bonds between the atoms.
½(nb-na) (No. of electron in bonding molecular orbital – no. of electron in anti bonding molecular orbital)

(ii) He₂ molecule does not exist, why? (2)
Answer:
Because bond order between two He atom is zero ie. No boncl between two He atoms so  He₂ cannot exist.

Question 18.
(i) Compressibility factor for ideal gas is (1)
Answer:
1 (one)

(ii) At 25°C and 760 mm of Hg pressure a gas occupies 600 mL volume. What will be its pressure at a height where temperature is 20°C and volume of the gas is 660 mL? (2)
Answer:

Question 19.
(i) Geographical representation of a gas law is given below.

(a) Name the gas law represented in graph.(1)
(b) State the above gas law. (1)
Answer:
(a) Boyles law
(b) At constant temperature the pressure of a given mass of gas is inversely proportional to volume.

(ii) Write ideal gas equation. (1)
Answer:
PV = nRT

Question 20.
(i) Name the thefrnodynamic system with exchange of energy and matter with surroundings. (1)
Answer:
Open system

(ii) State 1st law of thermodynamics. (2)
Answer:
Energy can neither be created nor be destroyed

Question 21.
(i) Define extensive property. (1)
Answer:
Extensive properties are those properties which depend upon amount of mass.

(ii) Identify extensive property from the following:
density, mass, pressure, volume. (2)
Answer:
Mass, volume.

Question 22.
(i) Oxidation number of oxygen atom in O₂ molecule is ………….. (1)
Answer:
Zero

(ii) In a reaction
2Cu₂O + Cu₂S → 6Cu + SO₂
Identify oxidising agent and reducing agent. (2)
Answer:
Oxidising agent – Cu₂O,
reducing agent – Cu₂S

Question 23.
(i) Represent the following compounds using stock notation:
(a) MnO
(b) FeO (1)
Answer:
(a)Mn(II)O
(b)Fe(II)O

(ii) What is oxidation and reduction in terms of oxidation number? (2)
Answer:
Oxidation – increase in oxidation number
Reduction – decrease in oxidation number

Question 24.
(i) Syn gas is a mixture of
(a) CO + H₂
(b) CO₂ + H₂
(c) CO + N₂
(D) CO₂ + N₂ (1)
Answer:
(a) CO + H₂

(ii) Write the difference between hard water and soft water. (1)
Answer:
Hard water do not lather with soap.
Soft water lather with soap easily.

(iii) Why Hydrogen peroxide is stored in wax lined glass vessels in dark? (1)
Answer:
Other wise H₂O₂ react with silica of glass and decomposes to oxygen.

Question 25.
(i) What are molecular hydrides? (1)
Answer:
Hydrides formed with p block elements.

(ii) Classify the following molecular hydrides into electron deficient, electron precise and electron rich hydrides:
NH₃, CH₄, B₂H₆, HF
Answer:
Electron deficient hydride : B₂H₆
Electron precise hydride : CH₄
Electron rich hydrides : NH₃, HF

Question 26.
(i) Name an alkali metal which forms superoxides.(1)
Answer:
Potassium – K

(ii) Write any two anomalous properties of Lithium.(2)
Answer:

• Lithium forms monoxide
• Lithium is hard

Question 27.
(i) Match the following:

Answer:

I. Limestone	a. Calcium Carbonate
II. Slaked lime	b. Calcium Hydroxide
III. Plaster of Paris	c. Calcium Sulphate H2O
IV. Quick lime	d. Calcium Oxide

(ii) Cement clinker is mixed with gypsum to form cement. What is the purpose of adding gypsum to form cement? (1)
Answer:
To control the setting time of cement.

Question 28.
(i) Write IUPAC names of the following: (2)

Answer:
(a) 2 – Methyl pentan-3-ol
(b) 4 – Oxo pentanoic acid

(ii). Identify groups with +R electron displacement effect from the following: (1)
-Cl, -COOH, -NO₂, -NH₂
Answer:
-NH₂, -Cl

Answer any 6 questions from 29 to 40. Each carries 4 scores. (6*4 = 24)

Question 29.
(i) State Heisenberg uncertainty principle. (2)
Answer:
It is impossible to measure both position and momentum of a moving microscopic particle.
Simultaneously and accurately

(ii) Name any four spectral lines of hydrogen atom.(2)
Answer:
Lyman series, Balmer series, Paschen series, Bracket series, Pfund series.

Question 30.
(i) Write the conclusions of Rutherford Alpha ray scattering experiment. (2)
Answer:
1. All atom has a small positively charged . nucleus at its centre.
2. Electrons are revolving round the nucleus.

(ii) Write two demerits of Rutherford atom model.(2)
Answer:
Demerits of Rutherford atom model are:
1. It couldn’t explain the stability of an atom.
2. It couldn’t explain the electronic structure of an atom.

Question 31.
(i) Write any two postulates of VSEPR theory. (2)
Answer:
1. The valence electron repel each other.
2. The repulsions are in the order lp – lp > lp – bp > bp – bp

(ii) Hydrogen bonds are of two types, which are they? Write one example for each. (2)
Answer:
(a) Intermolecular-H-bonding eg.
H₂0, HF, NH₃
(b) Intramolecular – H bonding eg.
O-nitrophenol

Question 32.
(i) Hybridisation of Carbon in CH₄ is
(A) sp²
(B) sp
(C) sp³
(D) sp³d (1)
Answer:
(C) sp³

(ii) Write any two characteristics of hybridisation.(1)
Answer:
(a) The number of hybrid orbitals formed is equal to the number of atomic orbitals undergo hybridisation.
(b) The hybrid orbitals are always equivalent in energy and in identical shape.

(iii) O₂ molecule is paramagnetic, explain using M.O. theory. (2)
Answer:
Due to the presence of unpaired electron in antibonding molecular orbital.

Question 33.
(i) Predict the effect of change of pressure in the following equilibrium: (2)

Answer:
No influence of pressure. Because no. of moles of reactant molecules and product molecules are equal.

(ii) Name and state the law used to predict effect of change in pressure in an equilibrium. (2)
Answer:
LeChatlier’s principle statment
It states that if a system at equilibrium is subjected to a change in concentration temperature, or pressure then the equillibrium shifts automatically in the direction that tends to nullify the effect of the change.

Question 34.
(i) Write Arrhenius concept of Acids and Bases. (2)
Answer:
According Arrhenius concept of Acids and Bases Compounds with H⁺ are called acids.
eg. HCl, HNO₃
Compounds with OH^– are called bases
eg. NaOH, KOH

(ii) Write conjugate acid and conjugate base of the following:
(a) H₂O
(b) NH₂ (2)
Answer:
(a) H₃O⁺ conjugate acid
OH^– conjugate base

(b) NH₄⁺ conjugate acid
NH₂^– congugate base

Question 35.
(i) What is diborane? (1)
Answer:
Hydride of boron

(ii) Name two types of bonds present in diborane molecule. (1)
Answer:

• Covalent bond 4 B-H bonds
• two 3 centered 2 electron bond or banana bond or two B-H-B bonds

(iii) Name two manmade silicates. (2)
Answer:
Asbestose, cements, glass

Question 36.
(i) Carbon monoxide is a poisonous gas. Why? (2)
Answer:
Carbon monoxide combines with haemoglobin to form carboxy haemoglobin. Which do not carry oxygen to the cell. This leads to death.

(ii) Name any two crystalline allotropes of carbon.(2)
Answer:
Diamond, Graphite

Question 37.
(i) Name any two elements detected by Lassaigne’s test. (2)
Answer:
Nitrogen, Halogen, Sulphur

(ii) Write two difference between Homolysis and Heterolysis. (2)
Answer:

Homolysis	Heterolysis
Fission occurs in such a way that epch atom in the bond gets one electron	Fission occurs in such a way that electrons are with one atom only
As a result of homqlysis free radicals are formed.	As a result of heterolysis, positive and negative ions are formed.

Question 38.

(a) Identify A and B. (1)
(b) Which is the major product in the above reaction? (1)
(c) Name and state the rule which decides the major product in the above reaction. (2)
Answer:

Markownikoffs rule.
The negative part of the addendum will move to the carbon atom which contains less number of hydrogen.

Question 39.
(i) Draw Newman’s projection formula for the conformers of ethane molecule. (2)
Answer:

(ii) Which conformer of ethane is more &Sbte?”Give reason. (2)
Answer:
Staggered.
Due to less repulsion between electrons.

Question 40.
(i) Name two gases responsible for greenhouse effect. (2)
Answer:
CO, CH₄

(ii) List two harmful effects of Acid rain. (2)
Answer:
Skin cancer, skin burning, pH change aquatic life affects.