2nd PUC Chemistry Model Question Paper 3 with Answers

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Karnataka 2nd PUC Chemistry Model Question Paper 3 with Answers

Time: 3.15 Hours
Max Marks: 70

Part – A

I. Answer all questions : ( 10 × 1 = 10 )

Question 1.
Define the term molality.
Answer:
Molality is defined as “The no of moles of solute present in 1 kg of solvent”.
OR
Molarity = \(\frac{\text { No. of moles of solute }}{\text { Mass of solvent in } \mathrm{kg}}\)

Question 2.
How does the enthalpy change during the formation of a non-ideal solution two liquids showing positive deviation from Raoult’s law?
∆H = +ve or enthalpy increases or heat is absorbed.

Question 3.
What is a primary electrochemical cell?
Answer:
A cell that cannot be recharged is called a primary cell.

Question 4.
For the reaction
2nd PUC Chemistry Model Question Paper 3 with Answers 1
what is the order?
Answer:
Zero order

2nd PUC Chemistry Model Question Paper 3 with Answers

Question 5.
What do you mean by selectivity of a catalyst?
Answer:
The ability of a catalyst to direct a reaction to give a particular product is called selectivity of a catalyst.

Question 6.
Give the chemical composition of Copper matte.
Answer:
Cu2S + Fes
OR
Cuprous sulphide + Ferrous sulphide.

Question 7.
Name the noble gas that is radioactive?
Answer:
Radon.

Question 8.
Write the general equation of the preparation of alkyl chlorides from alcohols using SOCl2.
Answer:
2nd PUC Chemistry Model Question Paper 3 with Answers 2

Question 9.
What are acetals?
answer:
Acetals are gem-alkoxy alkanes in which two alkoxy groups are present.

2nd PUC Chemistry Model Question Paper 3 with Answers

Question 10.
Name the water insoluble component of the starch?
Answer:
Amylopectin

Part – B

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

Question 11.
An element having atomic mass 60 amu, has FCC unit cell. The edge length of the unit cell is 4 × 102 pm. Find the density of the unit cell.
Answer:
2nd PUC Chemistry Model Question Paper 3 with Answers 3
d = 6.226 g/cm3

Question 12.
Write two applications of Kohlrausch law.
Answer:

  1. The degree of dissociation and dissociation constent of weak electrolyte can be calculated.
  2. Using this law, aim for both weak and strong electrolytes can be calculated.

Question 13.
The half-life period of a certain reaction is directly proportional to initial concentration of the reactant. Predict the order of the reaction and write the expression to calculate the half-life period of the reaction.
Answer:
Zero order – t 1/2 = \(\frac{[\mathrm{R}]_{0}}{2 \mathrm{k}}\)

2nd PUC Chemistry Model Question Paper 3 with Answers

Question 14.
Give two consequences of lanthanoids contraction.
Answer:
Due to lanthanoids contraction

  1. Similarity in atomic sizes of elements of second and third transition series.
  2. The separation of lanthanoids in piezo state become difficult.

Question 15.
Complete the following reaction;
i)
2nd PUC Chemistry Model Question Paper 3 with Answers 4
Answer:
2nd PUC Chemistry Model Question Paper 3 with Answers 5

ii) R – COOH → RCH2OH. Name the reagent used in the conversion?
Answer:
LiAlH2 in the presence of THF.

2nd PUC Chemistry Model Question Paper 3 with Answers

Question 16.
How does ketone react with ethylene glycol. Write chemical equation for the reaction.
Answer:
Ketones react with ethylene glycol in the presence of dry HCl gas to give a cyclic product known as ethylene glycol ketals.
2nd PUC Chemistry Model Question Paper 3 with Answers 6

Question 17.
What are analgesics? Give an example for non-narcotic analgesics.
Answer:
Analgesics are the chemical substances. which relieve the body pairs.
Ex: Asprin or paracetamol.

Question 18.
What are artificial sweeteners? Give an example.
Answer:
These are low calorie substances used as sweetening agents to replace sugar.
Ex: Saccharin / Aspartame / Alitanel. Sucralose.

Part – C

III. Answer Any FIVE of the following each questions carries three marks: ( 5 × 3 = 15 )

Question 19.
On the basis of Ellingham’s diagram . explain the principle of extraction of iron from its oxide ore. (3)
Answer:
2nd PUC Chemistry Model Question Paper 3 with Answers 7
Al 1073k, ∆G0 V/S T line for C → CO intersects the Fe → Feo line. Above 1073k, ∆G0 of C → CO becomes less than ∆G0 of Fe → Feo and hence carbon itself is oxidised to CO.
∴Carbon becomes very good reducing agent for the reduction of Feo to Fe at the temprature of 900k – 1500 k.
FeO(s) + C → Fe ↓+ CO ↑ At temp below 800 k. ∆G0 for CO → CO2 is less than Fe → Fe2O3 therefore CO is a better reducing agent for the reduction of Fe2O3 to FeO Fe2O3 + CO → 2FeO + CO2

2nd PUC Chemistry Model Question Paper 3 with Answers

Question 20.
Explain the principles involved in the manufacture of ammonia by Haber’s process. (3)
Answer:

  1. N2(g) + 3H2(g) ⇌ 2NH3(g)
  2. A/c to lechatelier’s principle, the forward reaction is favoured by low T and high P
  3. Optimum conditions in the process are 700k under 250 atmosphere and Iron catalyst containing K2O and Al2O3 promoter.

Question 21.
Complete the following equations; (1+1+1)
a) 5SO2 + MnO4+ 2H2O → 5 SO4 2-+4H+ +?
Answer:
5SO2 + MnO4+ 2H2O → 5 SO4 2-+4H+ + 2Mn2+ .

b) 5SO3 + Conc.H2SO4 → ?
Answer:
SO3 + H2SO4 → H2S2O7

c) 2nd PUC Chemistry Model Question Paper 3 with Answers 8
Answer:
2nd PUC Chemistry Model Question Paper 3 with Answers 9

Question 22.
a) Explain the action of Cone. HCl on KMnO4 crystals.    (2)
Answer:
When KMnO4 is treated with conc. HCl chlorine is liberated 2KMnO4 + 16 HCl → 2 Kl + 2MnCl2 + 8H2O + 5Cl2

b) Write the structure of perchloric acid.   (1)
Answer:
2nd PUC Chemistry Model Question Paper 3 with Answers 10

2nd PUC Chemistry Model Question Paper 3 with Answers

Question 23.
a) Transition metals show variable oxidation states. Explain (2)
Answer:

  • ns and (n -1) d subshells have almost same energy.
  • Both ns and (n -1) d electrons involve in bonding.

b) Which metal of 3d-series exhibit maximum number of oxidation state? (1)
Answer:
Manganese (Mn)

Question 24.
How is K2Cr2O7 manufactured from chromite ore. (3)
Answer:
Manufacture of K2Cr2O7 from chromite ore involves the following steps
Step – 1: Conversion of chromite ore into sodium chromate:
Chromite ore is heated with Na2CO3 in the presence of excess of air to form sodium chromate
4FeOCr2O3 + 8Na2CO3 + 7O2 → 8Na2CrO4 + 2Fe2O3 + 8CO2

Step – 2 : Conversion of sodium chromate into sodium di chromate.
The yellow solution of sodium chromate is filtered and acidified with H2SO4 to give a mixture of Na2 Cr2O7 and sodium sulphate
2Na2CrO4 + H2SO4 → Na2 Cr2O7 + Na2SO4 + H2O
The less soluble Na2SO4 is removed by filtration.

Step – 3 : Conversion of sodium bichromate into potassium dichromate:
The solution of sodium dichromate is treated with KCl to give potassium dichromate.
Na2Cr2O7 + 2Kcl → K2Cr2O7 + 2Nacl

Question 25.
Using valence bond theory (VBT), account for the geometry, type of hybridization and magnetic property of [NiCl4]2. (3)
Answer:
E.C of Ni = 28 = [Ar]18 3d8 4s2 4p0
E.C of Ni2+ = 28 – 2 = 26 = [Ar]18 3d8 4s0 4p0
2nd PUC Chemistry Model Question Paper 3 with Answers 11
When weak ligand at approaches the Ni2+ ion, it undergo SP3 hybridisation. The 4 hybrid orbitals overlap with orbitals of four CL – ligands.
2nd PUC Chemistry Model Question Paper 3 with Answers 12
Geometry: Due to SP3 hybridisation, the complex has tetrahedral structure
Magnetic Property: The complex is paramagnetic due to the presence of two unpaired electrons.

2nd PUC Chemistry Model Question Paper 3 with Answers

Question 26.
Define linkage isomerism of co-ordination compounds. Give an example. (3)
Answer:
Linkage isomerism is one in which two co-ordination compounds have the same molecular formula but differ in the mode of attachment of ligands to the central metal atom / ion
Ex: [CO (NH3) 5 (NO2)] Cl2 and [CO (NH3)5 (ONO)] Cl2

Part – D

IV. Answer Any THREE of the following each questions carries 5 marks. ( 3 × 5 = 15 )

Question 27.
a) Calculate the packing efficiency in BCC lattice.     (3)
Answer:
In a BCC unit cell, the edge length is ‘a’ and radius of the particle is ‘r’.
2nd PUC Chemistry Model Question Paper 3 with Answers 13
Then r = \(\frac{\sqrt{3}}{4}\)a
∴a = \(\frac{41}{\sqrt{3}}\)
and two particles are present in an unit cell of BCC
2nd PUC Chemistry Model Question Paper 3 with Answers 14
2nd PUC Chemistry Model Question Paper 3 with Answers 15

b) Calculate the number of particles per unit cell in FCC.   (2)
Answer:
No. of particles per unit cell of FCC
= \(\frac{1}{8}\)(No.of comer particles) + \(\frac{1}{2}\)(No.of facial particles)
= 1/8 × 8 = 1/2 × 6
= 1+3 = 4

2nd PUC Chemistry Model Question Paper 3 with Answers

Question 28.
a) Acetone boils at 56.38°C and a solution of 1.41g of an organic compound in 20 g of acetone boils at 56.88°C. Calculate the molar mass of the organic compound (Given kb for acetone = 1.67 k kg/mol). (3)
Answer:
W.K.T
2nd PUC Chemistry Model Question Paper 3 with Answers 16

b) What is reverse Osmosis, mention one important application of it.    (2)
Answer:
When a pressure larger then the osmotic pressure is applied on a concentrated solution. The solvent flows from concentrated solution to dilute solution through a semi permeable membrane is called reverse osmosis.
Application: It is used in desalination of sea water.

Question 29.
a) Standard EMF of the cell; Cu Cu2+(1M) Ag+(1M) Ag is 0.46 V at 25°C. Find the value of standard free energy change for the reaction that occurs in the cell. (3)
Answer:
W.K.T
∆G° = ηFE°cell
Where n = 2, E°cell = 0.46r, F = 96500 C
∆G°= -2 × 96500 × 0.46
= -108080 J
or – 108.08 KJ

b) Draw the neat labeled diagram of SHE and write its symbolic representation. (2)
Answer:
2nd PUC Chemistry Model Question Paper 3 with Answers 17
SHE is symbolically represent as Pt, H2 (lbar) /H+(1M).

2nd PUC Chemistry Model Question Paper 3 with Answers

Question 30.
a) Derive the integrated rate equation for a zero order reaction. (3)
Answer:
Consider a zero order reaction
R → P
Rate = \(\frac{-d[R]}{d t}\) = K[R]0
Rate = \(\frac{d[R]}{d t}\) = K × I
d[R] =-Kdt
Integrate on both sides
∫d[R] = -K∫dt
[R] = -Kt + I ………(1)
Where I is the integration constant
when t =o then [R] = [R]
∴[R]0 = K × 0 + I
∴I = [R]0
Substituting the value of I in eq (1)
[R] = -Kt + [R]0
Kt=[R]0 – [R]
K= \(\frac{[\mathrm{R}]_{0}-[\mathrm{R}]}{\mathrm{t}}\)

b) Give any two differences between order and molecularity of reaction.    (2)
Answer:
Molecularity:

  1. Molecularity is the no of reacting species under going simultaneous cousion in the elementary reaction.
  2. It always whole no.

Order:

  1. Order is the sum of the powers of the concentration terms in the rate law expression.
  2. It can be whole no. or fraction or even zero.

Question 31.
a) Write any two differences between lyophilic sols and lyophobic sols. (2)
Answer:
Lyophilic sols:

  1. Dispersed phase has greater affinity for dispersion medium.
  2. It is reversible.

Lyophobic sols:

  1. Dispersed phase has no affinity for dispersion medium.
  2. It is irreversible.

b) What are the differences between physisorption and chemisorption. (2)
Answer:
Physisorption:

  1. Adsorbate and adsorbent are held together by week vander wals forces.
  2. It is reversible.

Chemisorption:

  1. Adsorbatcand adsorbent are held together by strong chemical bonds.
  2. It is irreversible.

c) Give an example for homogeneous catalysis. (2 )
2nd PUC Chemistry Model Question Paper 3 with Answers 18

V. Answer Any FOUR of the following, each questions carries 5 marks. ( 4 × 5 = 20 )

Question 32.
a) i) Name the organic product formed when chloroalkane is heated with concentrated solution of sodium iodide (Nal) in acetone?
Answer:
Iodo alkane is formed

ii) Write the chemical equation for the above reaction
2nd PUC Chemistry Model Question Paper 3 with Answers 19

iii) Name the above reaction (1 + 1 + 1)
Answer:
Finkelstein reaction

b) Explain Fittig’s reaction with an equation. (2)
Answer:
When haloacene is heated with sodium metal in dry ethol medium higher aromatic hydrocarbon is formed.
2nd PUC Chemistry Model Question Paper 3 with Answers 20

2nd PUC Chemistry Model Question Paper 3 with Answers

Question 33.
a) Organic compounds A, B and C are aliphatic saturated hydroxyl compounds when they react with Lucas reagent (anhyd.ZnCl2 + conc. HCl), the following observations are made
i) Compound A gave turbidity immediately (1 + 1 + 1)
Answer:
A=Tertiary alcohol

ii) Compound B gave turbidity after five minutes.
Answer:
B = Secondary alcohol.

iii) Compound C gave turbidity only on heating, identify the type of compounds A, B and C.
Answer:
c = Primary alcohol.

b) Complete the equation:
2nd PUC Chemistry Model Question Paper 3 with Answers 21
Answer:
2nd PUC Chemistry Model Question Paper 3 with Answers 22

c) Name the main organic product formed when anisole is reacted with HI. (1)
Answer:
Phenol

Question 34.
a) Which of the following organic compound undergoes Cannizzaro’s reaction?    (1)
i) CH3CHO
ii) HCHO
Answer:
HCHO (Formaldehyde)

b) Write the mechanism of addition of HCN to a carbonyl compounds.m   (2)
Answer:
Step -1: Attack of nucleophile C
2nd PUC Chemistry Model Question Paper 3 with Answers 23

Step -2: Attack of proton:
2nd PUC Chemistry Model Question Paper 3 with Answers 24

c) Explain the conversion of carboxylic acid into an acid amide. Give the general chemical equation. (2)
Answer:
When carboxylic acids react with ammonia, gives ammonium salt which on heating gives acid amide
2nd PUC Chemistry Model Question Paper 3 with Answers 25

2nd PUC Chemistry Model Question Paper 3 with Answers

Question 35.
a) Explain Mendius reduction with an equation.    (2)
Answer:
Reduction of nitrites by sodium in alcohol to get a primary amine is called Mendius reduction
2nd PUC Chemistry Model Question Paper 3 with Answers 26

b) When aniline is treated with HNO2 at 273-278 K, benzene diazonium chloride is formed. Write the equation and name the reaction.   (2)
Answer:
2nd PUC Chemistry Model Question Paper 3 with Answers 27

c) What is Hinsberg’s reagent?
Answer:
Benzene sulphonyl chloride or C6H5 SO2 Cl is called Hinsberg reagent.

Question 36.
a) Write the Haworth’s structure of sucrose.   (1)
Answer:
2nd PUC Chemistry Model Question Paper 3 with Answers 28

b) What are non-essential amino acids?   (1)
Answer:
Aminoacids which can be synthesized by human body are called non-essential amino acids.

c) Name the heterocyclic N-containing base present only in DNA but not in RNA.   (1)
Answer:
Thymine

d) Vitamin – C cannot be stored in the body. Give reason.    (1)
Answer:
Excess of vitamin – C is excreted through urine.

2nd PUC Chemistry Model Question Paper 3 with Answers

Question 37.
a) Which among the following is a homopolymer and a co-polymer,   (2)
i) Nylon-6,6
ii)PVC
Answer:
i) Nylon 6,6 → Copolymer
ii) PVC → Homopolymer

b) How is Buna – N prepared? Write the equation.   (2)
Answer:
When 1,3- butadiene is heated with,acryloniteile, in the presence of sodium Buna – N is formed.
2nd PUC Chemistry Model Question Paper 3 with Answers 29

c) Give one example for a non-biodegradable polymer.
Answer:
PVC or any suitable example.