Download SGBAU BSc 2019 Summer 3rd Sem Chemisty Question Paper

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B.Sc. (Part-II) Semester—III Examination

CHEMISTRY

Time : Three Hours] [Maximum Marks : 80

Note :— (1) Question No. 1 is compulsory.

(2) Solve ONE question from each unit.

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(3) Draw diagrams and give equations wherever necessary.

(4) Use of scientific calculator is allowed.

1. (A) Fill in the blanks :(— 4x½=2

(i) The property of metals to form thin sheets on hammering is known as __________

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(ii) LiAlH₄ reduces the carbonyl group into __________ group.

(iii) The surface tension of liquid __________ with increase of the temperature.

(iv) The titration between an acid and the base is also called as __________

(B) Choose the correct alternative :— 4x½=2

(i) In conformational analysis of n-butane the highly stable conformation is :

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(a) Gauche (b) Anti or Skew

(c) Partially Eclipsed (d) Fully Eclipsed

(ii) The hybridisation of carbon and oxygen atoms in carbonyl group is :

(a) sp³ (b) sp

(c) sp² (d) dsp²

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(iii) The upper critical solution temperature of Phenol-water system is :

(a) 68.1 (b) 67.8

(c) 68.7 (d) 67.9

(iv) In gravimetric estimation the unknown compound is analysed by measuring its :

(a) Pressure (b) Volume

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(c) Density (d) Mass

(C) Answer the following in ONE sentence - — 4

(i) What is meant by resolution ?

(ii) What is phase transition ?

(iii) What are optically active compounds ?

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(iv) What is molality ?

UNIT—I

2. (A) Explain VSEPR theory with suitable example. 4

(B) How will you compare atomic orbitals with molecular orbitals ? 4

(C) Draw molecular orbital energy level diagram of O₂ molecule. Calculate its bond order. 4

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OR

3. (P) How will you differentiate bonding and antibonding molecular orbitals ? 4

(Q) Discuss (i) metallic luster (ii) Electrical conductivity of metal on the basis of free electron theory. 4

(R) Discuss the structure of BF₃ molecule on the basis of VSEPR theory. 4

UNIT—II

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4. (A) Calculate the mole fraction of ethanol and water, if solution contains 6 moles of ethanol and 3 moles of water 4

(B) Explain the terms :—

(i) Normality

(ii) Molality. 4

(C) Discuss the choice of suitable indicator in strong acid with weak base. 4

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OR

5. (B) Discuss the following steps involved in gravimetric estimation of Barium as barium Sulphate :

(i) Precipitation

(ii) Digestion. 4

(Q) Write a note on Iodimetry and Iodometry. 4

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(R) Explain :—

(i) End Point

(ii) Molarity. 4

UNIT—III

6. (A) Complete the following reactions :

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(i) H-C=CH + H₂O -->

(B) How will you prepare acetone from

(i) Isopropyl alcohol

(ii) 2, 2-Dichloro propane ? 4

(C) What happens when Benzoic acid is treated with :

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(i) Ethyl alcohol in presence of conc. H₂SO₄

(ii) PCl₅ in presence of conc. H₂SO₄ ? 4

OR

7. (P) How will you prepare

(i) Benzyl alcohol

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(ii) Phenyl cyanide. 4

(Q) What happens when

(i) Ethylene glycol on oxidation with chromic acid

(ii) Lactic acid reacts with ethanol in conc. H₂SO₄ ? 4

(R) Explain Aldol condensation in Aldehydes and Ketones with example. 4

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UNIT—IV

8. (A) Explain the following :

(i) Plane of symmetry

(ii) Centre of symmetry. 4

(B) Assign the following groups in proper priority order according to ‘R’ and ‘S’ nomenclature system :

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(i) —COOH, —NH₂, —OH, —CH₃

(ii) —C₂H₅, —OH, —H, —CH₃ 4

(C) What is geometrical isomerism ? Explain with suitable example. 4

OR

9. (P) Explain the conformational analysis of n-butane with energy level diagram. 4

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(Q) Explain the terms :

(i) Chirality

(ii) Racemisation. 4

(R) Classify the following compounds into E-Z type :

Br\ /Cl Br\ /H CH₃-C\ /CH₂ H CH₃-C\ /CH₂ -CH₃

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CH₃ Cl Cl Cl CH₃ CH₃ H

4

UNIT—V

10. (A) Explain the variation of Gibbs free energy with temperature and pressure. 4

(B) State and explain Nernst Distribution Law. State the conditions of its validity. 4

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(C) What is extraction ? Explain its types. 4

OR

11. (P) Derive Gibb’s—Duhem equation. 4

(Q) Explain the Phenol-Water system. 4

(R) The Value of Kp for Water

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CO(g) + H₂O(g) = CO₂(g) + H₂(g)

is 1.6 x 10⁻³ at 25°C. Calculate the standard free energy change (ΔG°) of the reaction at 25°C,

(R = 8.314 JK⁻¹ mole⁻¹) 4

UNIT—VI

12. (A) How relative viscosity of liquid is determined by Ostwald’s Viscometer ? 4

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(B) Define :—

(i) Cell constant

(ii) Molar conductance. 4

(C) 0.5 N solution of salt occupying volume between two platinum electrodes 0.0172 m apart and 0.04499 sq m. area has resistance 25 ohm. Calculate equivalent conductance of solution. 4

OR

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13. (P) What are the advantages of conductometric titrations over ordinary titrations ? 4

(Q) Explain the variation of specific and equivalent conductance with dilution. 4

(R) Describe moving boundary method for determination of transport number. 4