Kerala Plus One Chemistry Board Model Paper 2023 with Answers

Reviewing Kerala Syllabus Plus One Chemistry Previous Year Question Papers and Answers Pdf Model 2023 helps in understanding answer patterns.

Kerala Plus One Chemistry Board Model Paper 2023

Answer any 4 questions from 1 to 5. Each carries 1 score. (4 × 1 = 4)

Question 1.
The prefix for 10¹⁵ is ______
(a) peta
(b) nano
(c) pico
(d) femto
Answer:
(d) femto

Question 2.
What would be the lUPAC name for the element with atomic number 120?
Answer:
Unbinilium

Question 3.
The equilibrium constant for a reaction is ‘x’ for the forward direction. The equilibrium constant for the reverse reaction at the same temperature would be ______
Answer:
\(\frac{1}{x}\)

Question 4.
Write the IUPAC name of the compound given below.

Answer:
Hexane – 2, 5 – dione

Question 5.
The alkane which cannot be prepared by kolbe’s electrolytic method is ______
Answer:
Methane

Answer any 8 questions from 6 to 15. Each carries 2 marks.

Question 6.
(i) ‘Molarity of a solution depends upon temperature’. Justify this statement.
Answer:
Molarity depends on total volume of solution.
Volume depends on temperature

(ii) 4g of NaOH was dissolved in sufficient water to form 250 mL of the solution. Calculate the molarity of this solution. (1)
(Na = 23, O = 16, H = 1)
Answer:
Molarity(M) = \(\frac{\mathrm{W}_{\mathrm{B}} \times 1000}{\mathrm{M}_{\mathrm{B}} \times \mathrm{V}_{\mathrm{mL}}}\)
= \(\frac{4}{40}\) × \(\frac{1000}{250}\) = 0.4 mol/L

Question 7.
(i) What is photoelectric effect? (1)
Answer:
It is the ejection of electrons from the surface of a metal when radiations of suitable frequency strikes on it.

(ii) How is kinetic energy of the ejected electron in photoelectric effect related to the frequency of the electromagnetic radiation? (1)
Answer:
K.E = \(\frac{1}{2}\)mv² =h(v – v₀)
Kinetic energy proportional to frequency of light.

Question 8.
State Heisenberg’s uncertainty principle. Give its mathematical representation.
Answer:
It is impossible to measure both the position and momentum of a moving microscopic particle simultaneously and accurately.
∆x × ∆p >

Question 9.
What are isoelectronic species? Give two ions that are isoelectronic with Mg²⁺.
Answer:
Species which contains same number of electrons.
Al³⁺, Na+, Ne, F~, O₂ , N₃

Question 10.
Give two demerits of Mendeleev’s periodic table,
Answer:
1. Position of hydrogen was not clearly explained.
2. Increasing order of atomic weight was not followed every where eg. K & Ar

Question 11.
State the first law of thermodynamics and give its mathematical form.
Answer:
Energy can neither be created nor be destroyed
∆U = w + q
∆U – change in internal energy
q – quantity of heat absorbed
w – work done

Question 12.
Differentiate homogeneous equilibrium from heterogeneous equilibrium. Give an example for each.
Answer:
If the reactant and product are in same phase at equilibrium it is known as homogenous equilibrium.
eg. N_2(g) + 3H_2(g) → 2 NH_3(g)
If the reactant and product are in different phase at equillibrium it is known as heterogeneous equilibrium.
CaCO_3(s) → CaO_(s) + CO_2(g)

Question 13.
Identify the oxidation sate of chlorine in each of the following.
(a) ClO₃
(b) HCl
Answer:

Question 14.
Explain Carius method for the estimation of halogens in an organic compound.
Answer:
Carius Method: Organic compound is treated with dil. HNO₃ and silver nitrate. White precipitate is formed. It is filtered and weighed.
Percentage of halogen
= \(\frac{\text { Atomic mass of halogenxm × 100 }}{\text { Molecular mass of silverhalide × w }}\)

Question 15.
Draw the cis and trans isomers of the compound given below and label them correctly.
C₆H₅CH = CH-CH₃
Answer:

Answer any 8 questions from 16 to 26. Each : carries 3 scores. (8 × 3 = 24)

Question 16.
(i) How many volumes of water vapour would be produced if 12 volumes of dihydrogen gas reacts with 6 volumes of dioxygen gas? (1)
(ii) An organic compound is made up of 67.9% C, 5.70% H and 26.4% N. Calculate its empirical formula. (2)
Answer:

Question 17.
Calculate the frequency and wavelength of a photon emitted during a transition from n = 5 state to n = 2 state in the hydrogen atom.
Answer:

Question 18.
Define ionisation enthalpy. How does it vary in a period and in a group? Give reasons for your answer.
Answer:
Ionisation energy: It is the amount of energy needed to remove most loosely bound electron from a gaseous neutral atom.
Across the period ionisation enthalpy increases due to the decrease in size and increase in force of attraction.
Down the group Ionisation energy decreases due to the increase in size and decrease in force of attraction.

Question 19.
Explain intermolecular and interamolecular hydrogen bonding with an example.
Answer:
H bond is a bond formed by a H atom which is already attached to an electro negative atom again bonds with another electro-negative atom.
If the H-bond is between the two molecules it is known as intermolecular H-bonding. eg.H₂O, HF, NH₃.
If the H bond is within the same molecule it is known as intramoldecular H-bonding
eg. O-nitro phenol.

Question 20.
Discuss the hybridisation of phosphorous in PCl₅ molecule. Based on this, predict the shape and bond angles in it.
Answer:

axial Cl atom forms 90° bond angle and equatorial Cl atom forms with 120° bond angle.

Question 21.
Calculate the standard enthalpy of formation of benzene. Given

Answer:

Question 22.
(i) Consider the reaction 2A(g) ⇔ 2B(g) + C(g). Write the expression for K_c for this reaction.
(ii) If K_p for this reaction is 3.8 × 10^-6 at 1070 K, calculate K_p at this temperature. (2)
Answer:

Question 23.
Balance following redox reaction taking place in basic medium using oxidation number method.

Answer:

Balance all atoms other than hydrogen and oxygen
2MnO^–₄ + Br^– → 2MnO₂ + BrO^–₃
Balance the no.of oxygen atom
2MnO^–₄ + Br^– → 2MnO₂ + BrO^–₃ + H₂O
Add OH” to the deficient side since it is basic medium
2MnO^–₄ + Br^– + 2H₂O → 2MnO₂ + BrO^–₃ + H₂O
2MnO^–₄ + Br^– + H₂O → 2MnO₂ + BrO^–₃ + 2HO^–

Question 24.
(i) What are nucleophiles and electrophiles? (2)
Answer:
Electophiles: Electron loving species
eg: Cl⁺, BF₃, AlCl₃

(ii) Give an example each for charged and neutral nucleophiles. (1)
Answer:
Nucleophiles : Nucleus loving species,
eg: CN^–, NH₃

Question 25.
(i) State and illustrate Markovnikov rule with an example. (2)
Answer:
Markonikov’s rule:When an unsymmetric reagent is added to an unsymmetric alkene the negative part of the addentum gets attached to the carbon containing lesser number of hydrogen atom.

(ii) What are the products obtained when propene undergoes ozonolysis? (1)
Answer:

Question 26.
Identify the major products A, B and C in the following reactions.

Answer:

Answer nay 4 questions from 27 to 31. Each carries 4 scores. (4 × 4 = 16)

Question 27.
(i) What are quantum numbers? Explain any two quantum numbers. (3)
Answer:
Address of an electron.
1. Principal quantum no. (n): gives idea about energy and size of the orbital.
Values on n =1, 2, 3, 4 …. etc.
2. Azimuthal quantum number (l) – gives us shape of the subshell.
l can have values l = 0 to (n – 1) values. n = 2l = 0, 1 → s & p orbital.
n = 3 l, = 0, 1,2 → s, p and d orbital.
magnetic quantum no. (m) gives orientation of orbitals, m can have value -l to +l
l = 1 m = -1, 0, +1
spin quantum no. (s) gives us idea about spin of electrons. It can have values +½ or -½ .

(ii) Arrange 3d, 4s, and 3p in the increasing order of their energies. (1)
Answer:
3p < 4s < 3d < 4p

Question 28.
(i) Write the MO electronic configuration of N₂. (2)
Answer:
σ 1s² σ * 1s² σ 2s² σ * 2s² π2px² = π2py² σ2pz²

(ii) Calculate its bond order and predict the magnetic behaviour. (2)
Answer:
Bond order = \(\frac{1}{2}\)(N_b – N_a)

Question 29.
(i) What is Gibb’s free energy? (1)
Answer:
The ampount of enery which can be converted to be useful work is knows as Gibb’s free energy

(ii) Give the relation between Gibb’s free energy and enthalpy. (1)
Answer:
G = H – TS

(iii) Predict the spontaneity of a reaction in the following cases.
(a) ∆H and ∆S + v (high T) (1)
(b) ∆H = +ve; ∆S =-ve (1)
Answer:

Question 30.
(i) What are buffer solution? Given an example each for acidic and basic buffers. (2)
Answer:
Solution which resist the change in pH on addition of small amount of acid or alkali.

Acidic buffer – Mixture of weak acid + salt formed by weakacid with strong base, acetic acid + sodium acetate

Basic buffer – Mixture of weak base + salt formed by weak base with strong acid.
NH₄OH + NH₄Cl

(ii) What is the effect of dilution on the pH value of a buffer solution? Give reason. (1)
Answer:
pH of a buffer solution does not change on dilution. On dilution, due to buffer action the ratio of concentration of salt and acid or base remains unchanged.

(iii) Explain common ion effect. (1)
Answer:
The suppression of degree of dissociation of a weak electrolyte by the addition of a strong electrolyte containing a common ion.
Application of Common ion effect:
1. Purification of impure NaCl by using HCl
2. Salting out of soap from glycerol by using NaCl.

Question 31.
(i) Define resonance effect. (1)
Answer:
The polarity induced in a molecule by the interaction of a lone pair of electrons with a pi bond or the interaction of two pi bonds.

(ii) Explain the two types of resonance effect with suitable examples. (2)
Answer:
+ R Effect
Resonance effect which increases the electron density in a conjugated system with activating group.
eg:-OH, -OR, -NH₂, -F, – Cl etc.

-R Effect
Resonance effect which decreases the electron density in a conjugated system with deactivating group.
-NO₂, -CN, -COOH etc.

(iii) Which among the following is a group showing +R effect?
-CN, – OH, -NO₂, -COOH (1)
Answer:
+ R Effect: – OH