2nd PUC Chemistry Model Question Paper 1 with Answers

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Karnataka 2nd PUC Chemistry Model Question Paper 1 with Answers

Time: 3 Hrs 15 Min
Max. Marks: 70

Part-A

I. Answer all of the following. (Each question carries 1 mark) (10 × 1 =10)

Question 1.
Define VantHaffs factor.
Answer:
VantHaff’s factor is defined as “The ratio of normal molar mass to the abnormal molar mass”.

Question 2.
What are isotonic solutions?
Answer:
Two solutions having same osmotic at a given temperature are isotonic solutions

Question 3.
Mention the S.I unit for molar conductivity.
Answer:
s.m² mol^-1 or s cm² mol^-1

Question 4.
For the reaction A + B → products the rate becomes doubled when concentration of only A is increased by two times, the rate is increased by four times, when the concentration B is alone is doubled what is the order of the reaction?
Answer:
2 or two

Question 5.
Name the enzyme used in the inversion of cane sugar.
Answer:
Invertase

Question 6.
Name the method used for refining of Zirconium.
Answer:
Van – Arkel method

Question 7.
Complete the reaction
XeF₄ + O₂ F₂ → A + O₂ identify A.
Answer:
XeF₆

Question 8.
What is a Recemic mixture – ?
Answer:
An equimolar mixture of d and 1 isomrs is called recemic mixture.

Question 9.
Name the product obtained when acetaldehyde reacts with Hydroxyl amine.
Answer:
Acetaldoxime

Question 10.
Name the nitrogenous base present in RNA only.
Answer:
Uracil

Part-B

II. Answer any FIVE of the following. (Each question carries 2 marks) (5 × 2 = 10)

Question 11.
Silver forms CCP lattice and x-ray studies of its crystals show that the edge length of its unit cell is 408.6 pm. calculate the density of silver
Answer:

Question 12.
What is corrosion? Mention a general method to prevent it.
Answer:
The loss of metal in the form of its compounds due to the chemical attack by the environment is called corrosion of metal It is prevented

• By painting
• by alooying by cathodic protection

Question 13.
Write the Arrhenius equation and mention what each term stands for.
Answer:

K = A.e
Where K = rate constant
A = Arrhenices constant
Ea = Energy of activation
T = Temperature
R = Gas constant

Question 14.
Any two differences between lanthanides and Actinides.
Answer:
Lanthanides

1. 4 f – orbital is progressively filled
2. Only Pm (promethion) is radio active
3. They are less reactive

Actinides

1. 5f – orbital os progressively filled
2. All are radio active
3. They are more reactive

Question 15.
How does Acetyl chloride react with Anisol in presence of anhydrous aluminum chloride catalyst. Write the chemical equation of the reaction.
Answer:
When acetyl chloride is treated with anisole in the presence of anhydrous AlCl₃ catalyst, O and P – acetyl delivatives of anisole is formed.

Question 16.
What are the effects of the electron withdrawing and electron donating groups on acidity of carboxylic acids.
Answer:
Electron donating group decreases acidic strength and electron with drawing group increases acidic strength of carboxylic acids.

Question 17.
What are antacids? Give an example.
Answer:
The chemical substances which are used in the treatment of acidity are called antacids.
Ex: Ranitidine (Zantac)

Question 18.
What are food preservatives? Give one example.
Answer:
The chemical substances which prevent spoilage of food due to microbial growth are called food preservatives.
Ex: Table salt, sugar, Vegetable oils.

Part – C

III. Answer Any FIVE of the following. (Each question carries three marks) (5 × 3 = 15)

Question 19.
How is pure alumina obtained from Bauxite by leaching process?
Answer:
1. Bauxite contains impurities like
TiO₂ – Fe₂O₃ etc.
Bauxite is concentrated by digesting the powdered ore in a concentrated solution of NaOH at 473 – 573 K and 35 bar pressure. Al₂O₃ is leached as sodium aluminate.
The insoluble Fe₂O₃ and TiO₂ are removed by filtration.
H₂O₃ + α NaOH + 3H₂O → 2Na [A1 (OH)₄]

2. The solution of sodium aluminate is nutralized by passing CO₂ gas and the solution is seeded with treshly prepared Al₂O₃.
2Na[Al(OH)₄] + CO₂ → Al₂O₃ x H₂O + 2NaHCO₃

3. Hydrated alumina is filtered dried and heated to get pure Alumina Al₂O₃

Question 20.
Write the reactions that takes place during the manufacture of nitric acid by Ostwald’s process.
Answer:
Manufacture of HNO₃ by ostwald’s process involves 3 steps.

Step – 1: Oxidation of ammonia to NO

Step – 2 : Oxidation of No to NO₂
2NO_(g) + O_2(g) → 2NO_2(g)

Step – 3,
3NO_2(g) + H₂O_(I) → 2 HNO₃(q) + NO(g)

Question 21.
1. What happens when potassium chlorate is heated in presence of MnO₂. Write the equation for the reaction also.
Answer:
When potassium chlorate is heated in the presence of MnO₂ as a catalyst at 420K, oxygen is liberated.

2. draw the structure of sulphuric acid.
The structure of H₂SO₄ is

Question 22.
1. How is chlorine prepared by using MnO₂?
Answer:
Chlorine is prepared by heating MnO₂ with con HCl.
MnO₂ +4HCl → MnCl₂ + Cl₂ + 2H₂O

2. Complete the reaction NH₃ + Cl₂ (excess) →
NH₃ + Cl_{2 (excess)} → NCl₃ + 3HCl

Question 23.
d-block elements form co-ordination compounds. Give reasons.
Answer:
d-block elements form co-ordination compounds.
Reasons :

• They are small size of metals ions
• They have high ionic charges,
• Availability of d – orbitals

Question 24.
How is potassium dichromate pre¬pared from the chromite ore?
Answer:
The manufacture of K₂Cr₂O₇ from chromite ore involves is steps.
Step -1: 4 FeCr₂ O₄ + 8Na₂CO₃ + 7O₂ → 8Na₂ CrO₄ + 2FerO₃ + 8CO₂
Step – 2 : 2Na₂CrO₄ + 2H⁺ → Na₂Cr₂O₇ + 2Na⁺ + H₂O
Step – 3 : Na₂Cr₂O₇ + 2Kcl → K₂Cr₂O₇ + 2NaCl
OR
Complete explanation in 3 steps

Question 25.
Mention the geometry, magnetic property and type of hybridization in [Ni(cn)₄]^2- complex.
Answer:
Geometry : square planar complex Magnetic property: Diamagnetic Hybridisation: ASP²

Question 26.
Write any three postulates of Werner’s theory of complexes.
Answer:

1. Co-ordination compounds metals show two types of Valencies primary and secondary
2. Primary valencies are ionisable
3. Secondary valencies are non-ionisable

Part-D

IV. Answer any THREE of the following. [Each question carries 5 marks. (3 × 5 = 15)

Question 27.
a) Calculate the packing efficiency in body centered cubic crystals. (3)
Answer:
In a BCC unit cell the edge length is ‘a’ and radius of the particle is ‘r’. Then r = \(\sqrt{3} / 4 \mathrm{a}\) and two particles are present in an unit cell of BCC.

b. Calculate the number of particles per unit cells in f.c.c. (2)
No of particles per unit cell in
fcc = \(\frac { 1 }{ 8 }\) × 8 + \(\frac { 1 }{ 2 }\) × 6 =1 + 3=4

Question 28.
a) The boiling point of benzene is 353.23K. When 1.80 g of a non volatile, non electrolytic solute was dissolved in 90 g of benzene, the boiling point was raised to 354.11 K calculate the molar mass of the solute
[K_b for benzene = 2.53 K.kg mol^-1] (3)
Answer:

(b) Write two differences between ideal and non ideal solutions of two liquids (2)

Question 29.
a) Calculate the standard free energy change for the following reaction occurring in the galvanic cell at 298K
3Mg(S) + 2Al³⁺ (aq) → 3Mg²⁺ (aq) + 2 Al(S)
Given E⁰_Mg2+/Mg = -2.37 V and E⁰_Al3+/Al = -1.66V (4)
Answer:
Ecell = E⁰_R – E⁰_L
= -1.66 + 2.37
= 0.71 V
ΔG⁰ = -nFE⁰_cell
= -6 × 96500 × 0.71
= -411090 J or -411.09 KJ

b) What is primary battery?
Answer:
A battery which cannot be recharged and revised is called a primary battery.

Question 30.
a) Derive the integrated rate equation for the rate constant of a first order reaction. (4)
Answer:
Consider a first order reaction R → P

On integration, we get d[R]

In [R] = -Kt + I …………. (1)
Where I = Integration constant To calculate I,
t = 0,[R] = [R]₀
In [R]₀ = -k x 0 + I
I = in [R]₀
Substitute the value of I in eq² …………. (1)
In [R] = -Kt + In [R]₀

b) What is pseudo first order reaction? (1)
Answer:
A Chemical reaction in which order is one but molecularity is two or more is called pseudo unimolecular reaction.

Question 31.
a) Complete and balance the following reactions
SO₂ + H₂S oxidation →

FeCl₃ + H₂O hydrolysis → (2)

b) Mention two characteristics of enzyme catalysis (2)
Answer:

1. Highly efficient
2. Highly specific in nature

c) What is the sign of AS for the adsorption of gas on solids?
Answer:
ΔS decreases or ΔS = -Ve

Part – D

V. Answer any FOUR of the following. (Each question carries 5 marks) (4 × 5 = 20)

Question 32.
a) Explain SN1 mechanism by taking tertiary butyl bromide as an example.(3)
Answer:
SN¹ mechanism involves two steps

b) What is Wurtz Fitting’s reaction? Give an example. (2)
Answer:
Alkyl halide reacts with aylhalide in the presence of sodium in dry ether gives alkyl arenes.

Question 33.
a) How is phenol manufactured by cumene process. Give the chemical equations of the reaction involved. (3)
Answer:
Cumene is oxidised by oxygen to form cumene hydroperoxide. Which on acid hydrolysis gives phenol.

b) How do you prepare ethanol by using the Grignard Reagent? (2)
Answer:
When Grignard reagent is treated with HCHO addition product is formed which on hydrolysis gives ethanol

Question 34.
a) How is Benzol chloride converted into benzaldehyde? Name the reaction. (3)
Answer:
When benzoyl chloride on reduction with H₂ in the purence of palladium catalyst supported on barium sulphate benzaldehyde is formed

b) Write the chemical equation for the reaction between dilute NaOH and acetalhyde, mention the name of the product formed. (2)
Answer:

Question 35.
a) Explain how is Hinberg’s reagent is used to distinguish the primary, secondary and tertiary amines.
Answer:
Hinsberg’s reagent reacts with 1⁰ amine gives a product which is soluble in alkali.
Hinsberg’s reagent reacts with 2⁰ amine gives a product which is insoluble in alktali.
Hinsberg’s reagent doesnot react with 3⁰ amine.

b) Write the chemical reactions involved in the conversion of aniline into phenol (2)

Question 36.
a) What are carbohydrates? and how are they classified? (3)
Answer:
Carbohydrates are optically active polyhydroxy aldehydes or polyhydroxy ketones or those compounds which yield these on hydrolysis carbohydrates are classified into 3 types namely, monosaccharides, oligosaccharides and polysaccharides,

b) What is a peptide bond? How many peptide bonds are present in a tetra peptide?(2)
Answer:
The -CONH – bond formed b/w two α – amino acids is called peptide bond.

3 peptide bonds

Question 37.
a) 1. What are condensation polymers? Give an example.
Answer:
Condensation reacts b/w two different bifunctional or trifunctional monomeric units to give a polymer with the loss of simple molecules like H₂O NH₃ etc. is called condensation polymerisation. The polymers obtained are called condensation polymers.
Ex: Nylon 6.6, Dacron etc.

2. Give the IUPAC name of the monomer of natural rubber. (3)
Answer:
Isoprene or 2 – methyl – 1,3 – butadiene,

b) What are Biodegradable polymers? Give an example. (2)
Answer:
The polymers which decompose on it own during a certain period of time are called biodegradable polymers.
Ex : PHBV, Nylon – 2 – hycon – 6.