06.Sr_Chem.pdf

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BOARD OF INTERMEDIATE EDUCATIONSENIOR INTER CHEMISTRY

MODEL PAPER (English Medium)Time : 3 Hours (w.e.f. 2013 - 14) Max. Marks: 60

SECTION - ANote: (i) Very Short Answer type Questions.

(ii) Answer ALL the questions at one place in the same order.(iii) Each question carries TWO marks. 10 2 = 20

1. What are "Frenkel defects" in crystalline solids?2. What is "misch metal"? Give its composition and one use.3. State "Henry's law"?4. A solution of CuSO4 is electrolysed for 10 minutes with a current of 1.5

amperes. What is the mass of copper deposited at the cathode?5. What are "Matte" and Blister Copper"?6. What are "F centers"?7. What are "homopolymer" and "copolymer"?8. Write the names and structures of the monomers of the following polymers

(a) Dacron and (b) Teflon.9. What are "antibiotics"? Give 2 examples.10. What are "antihistamines"? Give 2 examples.

SECTION - BNote: (i) Short Answer type Questions.

(ii) Answer any SIX questions.(iii) Each question carries FOUR marks. 6 4 = 24

11. Calcualte (a) Molality (b) Molarity and (c) Mole fraction of KI, if thedensity of 20% (mass/ mass) aqueous KI is 1.202 g mL-1.(molar mass of KI = 166).

12. Explain the terms (a) Tyndall effect (b) Brownian movement (c) Krafttemperature and (d) gold number.

13. Explain briefly the extraction of aluminium from bauxite?

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14. (a) NO is paramagnetic in gaseous state but diamagnetic in liquid and solidstates. Why?

(b) Explain the structure of XeO3.15. What is Lanthanoid contraction? What are the consequences of Lanthanoid

contraction?16. Write a brief note on the structure of glucose.17. Explain the mechanism of Nucleophilic bimolecular substitution (SN2)

reaction with one example.18. (a) What is "Gatterman reaction"?

(b) pkb of aniline is more than that of methylamine. Why?SECTION - C

Note: (i) Long Answer type Questions.(ii) Answer any TWO questions.(iii) Each question carries EIGHT marks. 2 8 = 16

19. Give a detailed account of the collision theory of reaction rates of bimoleculargaseous reactions.

20. Explain a) Reimer - Tiemann reactionb) Williamson's Ether synthesisc) Hell Volhard Zelinsky reaction andd) Aldol condensation.

21. a) Explain briefly the manufacture of sulphuric acid by contact process.b) How is Chlorine prepared in the laboratory?How does it react with the following?a) H2S b) Na2S2O3 and c) Iron.



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ANSWERSSECTION - A

1. What are "Frenkel defects" in crystalline solids?Ans: The stoichiometric, point defect that arises when cation occupies interstitial site

instead of lattice sites in crystalline solids.e.g.: AgCl, AgBr.

2. What is "misch metal"? Give its composition and one use.Ans: Misch metal is an alloy of 95% Lanthanoid metal and 5% Iron and traces of S,

Ca, C and Al. It is used to make bullets.3. State Henry's law.Ans: At a given temperature, the partial pressure of a gas (p) (in vapour phase) is

directly proportional to the mole fraction of the gas (x) in the solution.p x p = KH . x

Where KH = Henry's law constant.

4. A solution of CuSO4 is electrolysed for 10 minutes with a current of 1.5amperes. What is the mass of copper deposited at the cathode?

63Ans: c = current = 1.5 amperes, E = 2E 63 1

e = = , t = time = 10 60 = 600 sec96,500 2 96,500 Mass of copper deposited (m) = c.e.t

1.5 63 600=

2 96,500 = 0.2938 grams.

5. What are "matte" and "Blister Copper"?Ans: The molten liquid obtained in reverberatory furnace contains mainly Cu2S and

little FeS is called "matte". The solidified Cu obtained in Bessemer converter having blisters (due to evolution of SO2) is called "blister copper".

6. What are "F centers"?Ans: The anion vacancies are occupied by the electrons in metal excess defect. These

electrons are responsible for colour and paramagnetic nature.



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7. What are "homopolymer" and "copolymer"?

Ans: Homopolymer: The polymer which is formed due to polymerisation of onekind of monomers.

H H

e.g.: n C2H4 ( C C ) n H H

Copolymer: The polymer which is formed due to polymerisatin of two ormore kinds of monomers.

e.g.: Nylon 6, 6 (monomers: Adipic acid & Hexamethylene diamine).8. Write the names and structures of the monomers of the following

polymers (a) Dacron and (b) Teflon.Ans: (a) DACRON:

Monomers: Ethylene glycol: HO CH2 - CH2 OH

Terepthalic acid: HOOC O COOH

(b) TEFLON:F F

Monomer: Tetrafluoro ethene: C = C

F F

9. What are "antibiotics"? Give 2 examples.

Ans: Antibiotic is the substance produced by chemical synthesis, which inhibits thegrowth or destroys disease causing microorganisms. Antibiotics either kill bacteria (bactericidal e.g.: Pencillin, Ofloxacin) or inhibit bacteria (bacterio-static e.g.: erythromycin, Tetracycline).

10. What are "antihistamines"? Give 2 examples.

Ans: The drug that prevents the interaction of histamine with the receptors of stomach wall are called "antihistamines".

e.g.: Seldane, Dimetane.



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SECTION - B11. Calculate (a) Molality (b) Molarity and (c) Mole fraction of KI, if the

density of 20% (mass/ mass) aqueous KI is 1.202 gm lit-1(molar mass of KI = 166).

mass 100Ans: Volume of the solution = = = 83.2 mldensity 1.202

Mass of solvent (water) = 100 - 20 = 80 g.Mass of solute 1000

a) Molality (m) = Gram molar mass of solute Mass of solvent20 1000

= = 1.51 mol/ kg.166 80Mass of solute 1000

b) Molarity (M) = gram molar mass of solute Volume of solution20 1000

= = 1.45 mol/ lit.166 83.2WH2O 80

c) no. of moles of water = nH2O = = = 4.44MH2O 18WKI 20

no. of moles of KI = nKI = = = 0.12MKI 166nKI 0.12Mole fraction of KI = = = 0.026.

nKI + nH2O 0.12 + 4.44

12. Explain the terms (a) Tyndall effect (b) Brownianmovement (c) Kraft temperature and (d) goldnumber.

Ans: (a) Tyndall effect: The phenomenonof scattering of light by colloidalparticles in all directions and for-mation of bright glowing cones isknown as "Tyndall effect".

(b) Brownianmovement: Thecontinous rapid zig-zag movement by colloidalparticles in the dispersion medium is known as"Brownian movement".



Brownianmovement

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(c) Kraft temperature: The temperature above which micelles are formed.(d) Gold number: The minimum number of milligrams of lyophilic colloid

required to prevent the coagulation of a standard gold sol on addition of 1 ml of 10% NaCl solution.

13. Explain briefly the extraction of aluminium from bauxite?

Ans: Al is extracted either from red bauxite (consists iron oxide impurities) or fromwhite bauxite (consists SiO2). Powdered ore is concentrated by leachal agentNaOH at 35 - 36 bar pressure and 473 - 523 K temperature to get sodium aluminate.

Al2O3 + 2 NaOH + 3 H2O 2 Na[Al(OH)4]Sodium aluminate is alkaline in nature, neutralised by CO2 gas.

2 NaAl(OH)4 + CO2 Al2O3 . x H2O + 2 NaHCO3Hydrated alumina is filtered, dried and ignited to give pure Al2O3.

1470 KAl2O3. x H2O Al2O3 + x H2O

Purified Al2O3 is added with CaF2 (Fluorspar) to lower the fusion temperatureand Na3AlF6 (Cryolite) is added to increase conductivity. This mixture is takenin steel vessel coated with carbon lining acts as cathode and graphite acts asanode and electrolysed.

2 Al2O3 + 3 C 4 Al + 3 CO2Reaction at Cathode: Al +3 + 3 e Al

Reaction at Anode: C + 2 O2 CO2 + 4 e

14. (a) NO is paramagnetic in gaseous state but diamagnetic in liquid andsolid states. Why?

(b) Explain the structure of XeO3.Ans: (a) NO has odd number of electrons (5 + 6 = 11 valencey e-). So NO is

paramagnetic in gaseous state. Where as in liquid & solid states NO exists

as N2O2 dimer and has even number of electrons (2 5 + 2 6 = 22valencey e-). So N2O2 is diamagnetic.



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(b) XeO3Xe = 5s2 5px1 5py1 5pz1 5d1 5d1 5d1 (3rd excited state)

hybridization bondsXe has one lone pair and six bond pairs. 3 bond pairs form 3 pi bonds. Xe undergoes sp3 hybridization. The shape of XeO3 is pyramidal. Bond angle is 103.

15. What is Lanthanoid contraction? What are consequences of Lanthanoidcontraction?

Ans: The gradual decreage in atomic radii & ionic radii of 14 Lanthanoid elements(with increasing atomic number) due to poor shielding of valence electronsand diffused shape of f orbitals is called "Lathanoid contraction".Consequences: Similarity of 4d & 5d elements. (e.g.: Zr & Hf) Difficulty in separation of Lanthanoides from their mixture due to similar

chemical properties and crystal structure.16. Write a brief note on the structure of glucose.Ans: The molecular formula of glucose is C6H12O6.

The formation of n - Hexane with HI & red P indicates straight chain forglucose.

HIOHC - (CHOH)4 - CH2OH CH3 - CH2 - CH2 - CH2 - CH2 - CH3 The formation of Oxime with NH2OH & the formation of cyanohydrin with

HCN indicates presence of C = O group. The formation of gluconic acid with Bromine water indicates presence of - CHO group.

CHO COOHBromine water(CHOH)4 (CHOH)4

CH2OH CH2OH

The formation of saccharic acid with HNO3 indicates presence of one primary-OH group.CHO

HNO3COOH

(CHOH)4 (CHOH)4CH2OH COOH



Xe

. .

OO

O

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The formation of pentaacetate with acetic anhydrate indicates presence offive -OH groups.

CHO CHOAcetic anhydride(CHOH)4 (CH COOCH3)4

CH2OH CH2 COOCH3 From these facts, open chain structure of glucose is

CHOH OH

HO H

H OH

H OH

CH2OH

17. Explain the mechanism of nucleophilic bimolecular substitution (SN2)reaction with one example.

Ans: Reaction of CH3Cl with OH- ion is the best example of SN2 mechanism. It is

a single step process. In this mechanism nucleophile displaces (substitutes) theleaving group in a single step and no intermediate compound is formed but transition state will be formed.

H H HOH +

HC Cl HO..... C ..... Cl HO C H + Cl

H H H H

Rate = K[CH3Cl] [OH-]It is a second order (as the rate of the reaction depends on concentration ofboth CH3Cl & OH

-) and bi molecular (as 2 molecules are taking part in therate determining step).Order of reactivity: 1- alkyl halide > 2- alkyl halide > 3- alkyl halide.

Effect of leaving group: RI > RBr > RCl > RF.

Stereochemistry: Complete inversion of configuration takes place. It is liketurning of inside of umbrella out when caught in strong wind.



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18. a) What is "Gatterman reaction"?b) pkb of aniline is more than that of methylamine. Why?

Ans: (a) Gatterman reaction: The reaction in which diazonium group of diazonium salt is replaced by the nucleophiles like Cl- or Br- or CN- in presence of corresponding halogen acid & Cu powder.

N2Cl Cl

Cu + N2 + CuClHCl

. .

(b) H - N - H H . .

H - C N - H

H H

In aniline, electron pair presents on N is involved in conjugation (resonance)and is less available for protonation than that of methyl amine. So aniline isless basic i.e. lowest kb or highest pkb. Therefore pkb of aniline is more thanthat of methylamine.

SECTION - C19. Give a detailed account of the collision theory of reaction rates of

bimolecular gaseous reactions.Ans: This theory was proposed by Arrhenius and developed by Max Trautz &

William Lewis to explain the rates of gaseous reactions. It is based on kinetic molecular theory of gases. According to this theory the reactant molecules are assumed to be hard

spheres. Collisions must takes place between reactants (molecules) to occur a

reaction. Collisions are possible if 2 or more molecules are present. The minimum energy must be possessed by the reactant.

Molecules to give products is called "threshold energy (ET)". Molecules having other than threshold energy are called "normal

molecules". Collisions between normal molecules are called "normal collisions", which

do not lead the chemical reaction, hence products are not formed.



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In addition to the normal molecules, the molecules must acquire some extraamount of energy, called " activation energy (Ea)".

Ea = ET - ER.

The molecules possesing threshold energy are called "activated molecules". Proper orientation of reactant molecules lead to bond formation and

products are formed. Collisions occuring between activated molecules with proper orientation

are called "effective collisions". Effective collisions are less in number when compared to normal collisions. The number of collisions per second per unit volume of the reaction

mixture is known as collision frequeny (Z). Activation energy also affectsthe rate of a reaction.

For a bimolecular elementary reactionA + B ProductsRate = P.ZAB . e

-Ea/ RT

ZAB = Collision frequency of reactants A & B.P = Probability (steric) factor.Ea = Activation energy.R = Universal gas constant. Rate of a reaction is determined by Ea & proper orientation of the

molecules.Drawbacks:

It considers atoms or molecules as hard spheres. It ignores structural aspect of molecules.



P.

E.

ET Ea

E

ER

EP

Reaction coordinate

P.E.

ET

E

ER

EP

Reaction coordinate (Exothermic reaction) (Endothermic reaction)

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20. Explaina) Reimer - Tiemann reaction b) Williamson's ether synthesisc) Hell - Volhard - Zelinsky reaction and d) Aldol condensation.

Ans: a) Reimer - Tiemann reaction: In this reaction phenol is converted into salicylaldehyde when phenol is treated with CHCl3 and aq. NaOH or aq.KOH.

OH OH

65C CHO

+ CH Cl3 + 3 Na OH + 3 NaCl + 2 H2O

b) Williamson's ether synthesis: Symmetrical and unsymmetrical ethers are prepared by the reaction between alkyl halide and sodium alkoxide.C2H5O Na + I C2H5 C2H5OC2H5 + NaI

c) Hell - Volhard - Zelinsky reaction: The reaction in which halogenationtakes place at alpha position of a carboxylic acid (having alpha hydrogen)when treated with a halogen (Cl2 or Br2) in presence of red phosphorus.

HRed Phosphorus

H

H3C C COOH H3C C COOH + HCl

H + Cl ClH2O Cl

d) Aldol condensation: The condensation of same aldehydes (having alphahydrogen) in presence of dilute alkali to form hydroxy aldehyde (aldehyde + alcohol) is called "Aldol condensation".

O H dil. NaOH

OH H

H3C C + H C CHO H3C C C CHO (Aldol)H H H H

21. a) Explain briefly the manufacture of Sulphuric acid by contact process.b) How is Chlorine prepared in the laboratory. How does it react with thefollowing?a) H2S b) Na2S2O3 and c) Iron

Ans: a) Manufacture of H2SO4 (Contact process)H2SO4 is manufactured by contact process in 3 stages as follows:1) Burning of S or sulphide ore in air to give SO2.



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S + O2 SO24 FeS2 + 11 O2 2 Fe2O3 + 8 SO22) Oxidation of SO2 to SO3 at optimum pressure 2 bar & optimum

temperature 720 K in presence of a catalyst V2O5.V2O52 SO2 + O2 2 SO3; H = - 19.6 KJ/mol.

3) Absorption of SO3 by H2SO4 to give oleum.SO3 + H2SO4 H2S2O7 (oleum)Oleum on dilution with water gives H2SO4.H2S2O7 + H2O 2 H2SO4

b) Preparation of Cl2 (Lab Method):Cl2 can be prepared by heating MnO2 with conc. HClMn O2 + 4H Cl 2 H2O + Cl2 + MnCl2

Reactions:a) Cl2 reacts with H2S to produce HCl & S.

Cl2 + H2 S 2 HCl + Sb) Cl2 reacts with Na2S2O3 to give Na2SO4.

Cl2 + H2 O + Na2S2O3 2 HCl + Na2SO4 + Sc) Cl2 reacts with Fe to give FeCl3.

2 Fe + 3 Cl2 2 FeCl3.A.N.S.Sankara Rao, Senior Lecturer.



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06.Sr_Chem.pdf