Kerala Plus One Chemistry Board Model Paper 2022 with Answers

Reviewing Kerala Syllabus Plus One Chemistry Previous Year Question Papers and Answers Pdf Model 2022 helps in understanding answer patterns.

Kerala Plus One Chemistry Board Model Paper 2022

Answer any 8 questions from 1 to 11. Each carries 2 scores: (8 × 2 = 16)

Question 1.
Write any two properties of cathode rays. (1)
Answer:

• They contain materjal particle.
• They move in straight line.

Question 2.
i) Mention the principle which restricts the number of electrons in an orbital as two. (1)
Answer:
Pauli’s Exclusion principle

ii) Define orbital (1)
Answer:
Orbitals are the region where the probability of finding an electron is maximum.

Question 3.
Explain sp³ hybridisation. Give an example of a molecule in which the central atom is in sp³ hybridisation.
Answer:
One s-orbital and three p-orbital hybridises to form four sp3 hybrid orbitals of same shape and energy, eg: CH₄, NH₃, H₂O.

Question 4.
Explain the structure of H₂O molecule on the basis of VSEPR theory.
Answer:
In H₂O, sp³ hybridisation occurs and the geometry is tetrahedral with bond angle 109°. 281 but due to the presence of two lone pair of electrons repulsion occurs and bond angle is reduced to 104.5°. Shape changes to bent shape. .

Question 5.
i) Define oxidation and reduction in terms of oxidation number.
Answer:
Oxidation – increase in oxidation number
Reduction – decrease in oxidation number.

ii) Identify the oxidising and reducing agent in the following redox reaction.
Zn + Cu²⁺ → Zn²⁺ + Cu (1)

Reducing agent – Zn- undergoes oxidation Oxidising agent -Cu²⁺ undergoes reduction.

Question 6.
i) Which one of the following is an electron precise covalent hydride? (1)
(a) CH₄
(b) B₂H₆
(c) H₂O
(d) NH₃
Answer:
(a) CH₄

ii) What is Calgon? (1)
Answer:
Sodium hexa metaphosphate – calgon

Question 7.
Match the following:

Answer:

Question 8.
Discuss the structure and bonding in diborane (B₂H₆) molecule.
Answer:


Four terminal B-H bond – 2 centered -2 electron bond. Two B-H-B-3 centred 2 electron bond or bridge bond.

Question 9.
i) Write the IUPAC name of

Answer:
3-chloropropanal

ii) Draw the structure of pent-3-en-2-ol. (1)
Answer:

Question 10.
i) Arrange the following carbocations in the increasing order of their stability. (1)

Answer:

ii) Name the factors which influence the stability of carbocations. (1)
Answer:
Inductive effect, hyper conjugation

Question 11.
Mention any two applications of green chemistry in day to day life.
Answer:
1. biodegradable polymers
2. for bleaching purpose H₂O₂ is used.

Answer any 8 questions from 12 to 23. Each carries 3 scores: (8×3 = 24)

Question 12.
A compound contains 4.07% hydrogen, 24.27% carbon and 71.65% chlorine. Its molar mass is 98.96 g. What are its empirical and molecular formulas?
Answer:

Empirical formula CH₂Cl
Empirical formula mass = 12 + 2 + 35.5 = 49. 5
Molecular mass = 98.96
n = \(\frac{\text { Molecular mass }}{\text { Empirical formula mass }}\) = \(\frac{98.96}{49.5}\) = 2
Molecular formula = Empirical formula × n
= (CH₂Cl₂)₂
MF = C₂H₄Cl₂

Question 13.
i) Distinguish molarity and molality of solution. (2)
Answer
Molarity (M) is defined as the number of moles of solute in one litre’of the solution.
M = \(\frac{W_B}{M_B}\) × \(\frac{1000}{V in ml}\)

W_B → weight of. solute
M_B → Molecular mass of solute
V → Volume of solution

Molality (m): Molality is defined as the no. of moles of solute in one kilogram of the solvent.
m = \(\frac{W_B}{M_B}\) × \(\frac{1000}{W_A in g}\)
W_B → Weight of solute
M_B → Molecular-mass of solute
W_A → Weight pf solvent in gram.

ii) Among molarity and molality which one is tem-perature dependent? (1)
Answer:
Molarity is temperature dependent.

Question 14.
i) What are representative elements? (1)
Answer:
Representative elements: s block elements and p block elements together known as representa¬tive elements.

ii) What are isoelectronic species? Give suitable examples. (2)
Answer:
Isoelectronic species: Species which contains same number of electrons.
N^3-, O^2-, F^–, Na⁺, Mg²⁺, Al³⁺ – All contains 10 electrons.

Question 15.
i) Define electron gain enthalpy. (1)
Answer:
It is the enthalpy change when an electron is 20 added to an isolated gaseous atom

ii) Chlorine has more negative electron-gain enthalpy than flourine. Explain. (2)
Answer:
In flourine new electron is added to 2p orbital, the repulsion is more. In chlorine the new electron is added to 3p orbital due to large size of 3p orbital repulsion is less.

Question 16.
Write the postulates of kinetic molecular theory of gases.
Answer:
The important postulates of Kinetic molecular theory are:

• All gases contains small, minute, large no.of particles called mblecules.
• Molecules are in random motion.
• During their motion they collide with each other and also with the walls of the container. This creat pressure.
• The volume of the gas molecules is negligible as compared to the total volume of the gas.
• There is no force of attraction between the gas molecules.
• Average kinetic energy of the molecules is directly proportional to its absolute temperature.

Question 17.
i) A vessel of 120 ml capacity contains a certain amount of gas at 35°C and 1.2 bar pressure. The gas is transferred to another vessel of volume 180 ml at 35°C. What would be its pressure? (2)
Answer:
\(\frac{P_1 V_1}{T_1}\) = \(\frac{P_2 V_2}{T_2}\) , \(\frac{1.2 \times 120}{308}\) = \(\frac{P_2 \times 180}{308}\)
P₂ = \(\frac{1.2 \times 120}{180}\) = 0.8 bar

ii) What is the effect of temperature on viscosity of liquids? (1)
Answer:
Viscosity decreases with increase in temperature.

Question 18.
i) An example for intensive property is
(a) Mass
(b) Volume
(c) Density
(d) Heat capacity
Answer:
(c) Density

ii) Calculate standard enthalpy of formation (AH°_r) of CO from the following data using Hess’s law. (2)

Answer:

Question 19.
Account for the following:
i) AlCl₃ can act as Lewis acid. (1)
Answer:
AlCl₃ is an electron deficient compound ie. it behaves as Lewis acid.

ii) pH of NH₄Cl in water is less than 7. (1)
Answer:
NH₄Cl + H₂O → NH₄OH + HCl
ie. NH₄CI is a salt of weak base and strong acid hence the pH is less than 7 indicating acidic nature.

iii) Addition of acetate ions to acetic acid decreases the concentration of hydrogen ions [H⁺] (1)
Answer:
Due to common ion effect.

Question 20.
i) Name the different types of redox reactions. (2)
Answer:
i) Disproportionation reaction, Combination reaction Displacement reaction, Decomposition reaction.

ii) Write the chemical reaction takes place when Zn rod is dipped in dil HCl. (1)
Answer:
Zn_(s) + HCl → ZnCl₂ + H₂

Question 21.
i) What is temporary hardness? (1)
Answer:
i) Temporary hardness can be removed easily.

ii) Suggest two methods for the removal of temporary hardness. (2)
Answer:
a) Boiling: On boiling bicarbonates of calcium and magnesium are precipitated as carbonates and is filtered off.
b) Clarks process: By adding lime water (Ca(OH)₂) corresponding carbonates are precipitated and is filtered off.

Question 22.
i) Write the major and minor products formed in the following reaction:
CH₃ – CH = CH₂ + H – Br → (2)
Answer:

ii) Write the rule which governs the formation of major product. (1)
Answer:
Markonikovs rule

Question 23.
Define the following terms:
i) Green house effect. (1)
Answer:
Due to the lack of plants and trees, the CO₂ level of earth’s atmosphere increases and it keeps the ultraviolet radiations in the earths atmosphere. So the temperature increases and ice bergs melts.

ii) Biological Oxygen Demand(BOD) (1)
Answer:
Biological Oxygen Demand (BOD): It is the amount of oxygen needed to degrade organic matter.

iii) Eutrophication. (1)
Answer:
Eutrophication: Due to the presence of phosphates and nitrates the algae and unwanted plants grow easily and it absorbs the dissolved oxyg6n in the water. It affects the aquatic life. This is known as eutrophication.

Answer any 5 questions from 24 to 31. Each carries 4 scores: (5 × 4 = 20)

Question 24.
i) Discuss the postulates of Bohr model of hydrogen atom. (3)
Answer:

• The electrons in an atom are revolving around the nucleus in circular path called orbits.
• As the electrons remain in a particular orbit, it does not lose or gain energy.
• Energy is emitted or absorbed by an atom only when an electron in it moves from the orbital to higher or lower levels.
  ∆E = E₂ – E₁ = hv
• Only those orbits are permitted in which the angular momentum of the electron is a whole no. multiple of \(\frac{h}{2π}\).

ii) Using s, p, d, f notations describe the orbital with the following quantum
a) n = 2, l = 1 (1A)
b) n = 3, l = 2 (1A)
Answer:
a) 2p
b) 3d

Question 25.
i) Represent the MO configuration of N₂ molecule. (2)
Answer:
M.O configuration of N₂ is:

ii) Differentiate intermolecular and intramolecular hydrogen bonding using suitable example. (2)
Answer:
Intermolecular H-bonding: If the hydrogen bond is between the two molecules it is called inter-molecular-H-bonding.
eg: H₂O, HF

Intramolecular H-bonding: If the hydorgen bond is within the molecule. It is called inttramolecular -H-bonding.
eg. Ortho-nitrophenol.

Question 26.
i) State the first law of thermodynamics and write its mathematical expression. (2)
Answer:
“Energy can neither be created nor be destroyed” ’Au=q+w

ii) Define Gibb’s energy. (1)
Answer:
Gibbs free energy: The amount of energy which can be converted to useful work.

iii) Give the relationship between the Gibbs energy change (∆G) and entropy change (∆S) of a reaction.
Answer:
∆G = ∆H – T∆S

Question 27.
i) State Le-Chatelier’s principle. (1)
Answer:
If a system in equilibrium is subjected to change in concentration temperature or pressure the equillibrium shifts in the direction that tends to reduce the effect of the change.

ii) Di hydrogen gas is obtained from natural gas by partial oxidation with steam as per following endothermic reaction.
CH_4(g) + H₂O_(g) → CO_(g) + 3H_2(g)
Write an expression for K_p for the above reaction (1)
Answer:

iii) Describe the effect ofthe following in the equilibrium
CH_4(g) + H₂O_(g) → CO_(g) + 3H_2(g)
a) Increasing the pressure. (1)
b) Increasing the temperature. (1)
Answer:
In forward reaction the number of moles increases.
(a) So increasing pressure favours backward reaction
(b) forward reaction is endothermic so it favours high temperature

Question 28.
i) Describe the solvay process for the manufacture of sodium carbonate. (Na₂CO₃.10H₂O). (2)
Answer:
Solvay process: By passing C02 through
ammonical brine solution sodiumbicarbonate is obtained. It is filtered and heated to get sodium carbonate.

ii) Beryllium shows anomalous properties. Given reason. (2)
Answer:
Small size, high ionisation energy and absence of vacant d orbitals.

Question 29.
i) What is borax bead test? (2)
Answer:
When borax is heated with transition metals beads with characteristic colours are obtained.

ii) CCl₄ cannot be hydrolysed by water. Why?
Answer:
In CCl₄ there is absence of vacant d orbitals.

iiii) CO₂ is a gas but SiO₂ is a solid. Explain. (1)
Answer:
In CO₂ the force between the each molecule is weak vander walls force and the hybridisation is sp which gives linear shape. So it is gas.
In SiO₂ the hybridisation is sp² each Si atom is tetrahedrally connected to oxygen atom.So it has three dimenstional network. So SiO₂ is solid.

Question 30.
i) Name a method used for the estimation of nitro-gen in an organic compound.
Answer:
Kjeldahl’s Method or Dumas Method

ii) How will you detect the presence of chlorine in an organic compound?
Answer:
To the sodium fusion extract add one or two drops of nitric acid and add 1 ml of AgNO₃ solution curdy white precipitate is obtained. This indicates presence of chlorine.

iii) Suggest a method used for the separation of chlo¬roform and aniline. (1)
Answer:
Distillation.

Question 31.
i) Discuss the Huckel rule for aromaticity. (2)
Answer:
For a compound to be aromatic
It should be cyclic, conjugated, planar and should contain (4n +2) no. of pi electrons in the ring.

ii) Draw the Sawhorse projection formula for the eclipsed and staggered conformations of ethane. (2)
Answer: