C-MN8-U-CHM

CHEMISTRY

PAPER-I

I Time Allowed : Three Hours I Maximum Marks 200 I

QUESTION PAPER SPECIFIC INSTRUCTIONS

Please read each of the following instructions carefully before attempting questions

There are EIGHT questions in all, out of which FIVE are to be attempted.

Question Nos. 1 and 5 are compulsory. Out of the remaining SIX questions, THREE are to be attempted selecting at least ONE question from each of the two Sections A and B.

Attempts of questions shall be counted in sequential order. Unless struck off, attempt of a question shall be counted even if attempted partly. Any page or portion of the page left blank in the Question-cum-Answer Booklet must be clearly struck off.

All questions carry equal marks. The number of marks carried by a question/part is indicated against it.

Answers must be written in ENGLISH only.

Unless otherwise mentioned, symbols and notations have their usual standard meanings.

Assume suitable data, if necessary, and indicate the same clearly.

Neat sketches may be drawn, wherever required.

h = 6 ·626 x 10-34 Js

R = 8·314 J K-1 mol-1

c = 3 x108 ms- 1

N A = 6 ·023 X 1023

1

k 8 =1 ·38 x 1o-23 JK- 1

7t=3·14

F =96500 C

1 atm = 101325 Pa

[ P.T.O.

www.examrace.com

SECTION-A

1. (a) Explain why-

(i) the bond angle in F 20 is smaller than that in H20;

(i i) certain substances like CO and N20 are associated with residual entropy even at 0 K. 5+5

(b) (i) Assuming that the activation energy and pre-exponential factor are temperature independent, obtain the expression relating the activation energy (Ea) and the rate parameters k(1J.) and k(T2 ) for the same reaction at temperatures 7i and T2 .

(ii) Calculate the ionic strength of a solution that contains 0 ·01 mol kg- 1

H2S04 and 0·02 mol kg- 1 sodium chloride. 5+5

(c) The heat of the reaction

Fe20 3 (s) +3H2 (g) -7 2Fe(s) +3H20(1)

at 25 °C was found to be -8 · 4 kcal. What will be the heat of the reaction at 120 °C? The molar heat capacities at constant pressure and at

25 oc for iron oxide, hydrogen, iron and water are 25 · 0 cal deg - l mol-1,

6 ·9 cal deg- 1 mol- 1, 6·1 cal deg- 1 mol- l and 18·0 cal deg- 1 mol- l

respectively.

(d) (i) How many crystal systems are there? Name the crystal systems wherein the unit cell axes are mutually perpendicular. Give one example in each case.

(ii) What is the equation for the distance between the planes ( 11 0) for a crystal

10

with mutually perpendicular axes? 5+5

2. (a) Explain the following : 5+5+10

(i) The dipole moment of CF4 is less than that of CH2F 2 .

(ii) Carbon dioxide has a linear structure whereas sulphur dioxide is a bend molecule.

(iii) The bond order of NO is lower than that of NO+. Comment on their magnetic behaviour.

(b) A molecule has only two translational and two vibrational energy levels. Show that the molecular partition function can be written as the product of two partition functions. 10

(c) Explain the adsorption theory of catalysis. What are the various steps involved in it? Give one example to support your answer. 10

2

www.examrace.com

3. (a) (i) Discuss the principle of polarographic analysis. Explain the meaning and significance of half-wave potential (E %). If E y

2 values of two electroactive

species are too close, how can these be separated?

(ii) "Magnetic susceptibility measurements are of little use in structural elucidation of lanthanide complexes." Justify the statement. 10+ 10

(b) (i) Just define the terms phase, component and degree of freedom involved in the statement of phase rule.

(ii) How many components are there in an aqueous solution of NaCl and KBr? If to this solution KCl and NaBr are added, how many components will be there? 5+5

(c) kl

The 'relaxation time' for a reversible first-order reaction C D is k._l

100. microsecond and the equilibrium constant is 1· 0 x 10 2 . Find k1 and k_1. 10

4. (a) (i) State and explain Einstein law of photochemical equivalence. How is low quantum yield explained?

(ii) The volume of nitrogen gas at 1 atmosphere and 273 K required to

cover one gram of silica gel is 0 ·129 dm 3 . Calculate the surface area

of the gel if each nitrogen ｾｯｬ･｣ｵｬ･＠ occupies an area of 16·2x 10- 10 m 2 .

(Given NA =6·023x 1023) 10+10

(b) Consider a galvanic cell that uses the reaction

Cu (s) + 2Fe3 + (aq) -7 2 Fe2+ (aq) +Cu 2 + (aq)

• 0 0

Gtven, EFe3+ /Fe2+ = +0· 77 V and E Cu2+ fCu = +0·34 V.

(i) Calculate the standard cell potential.

(ii) Obtain the cell potential at 25 °C that has the following concentration

values

[Fe3 +]=1·0 x10-4 M; [Cu2+]=0·25 M; [Fe2 +]=0·2 M

(Given, F =96500 C, R = 8 ·314 JK-1 mol- 1)

(c) Set up the Schrodinger wave equation (three dimensions). Comment on the nature of the equation and various terms involved. Explain the significance

10

of 'II and w2. 10

3 [P.T.O.

www.examrace.com

5 . . (a)

(b)

(c)

SECTION-B

Explain the following briefly

(i) Fluorescence

(ii) Chemiluminescence

Explain the following terms

(i) Chelate effect

(ii) Lability

Explain why-

(i) the absorption spectra of actinides (ions) are independent of the nature of the ligand attached to them;

(ii) Co2 + salts are stabler than those of Co3 + salts, but solutions of Co2 +

complexes get readily oxidized to Co3+ complexes. (At. No. of Co is 27)

(d) (i) Draw neat diagrams of the shapes of d-orbitals.

(ii) Explain the pattern of splitting of d-orbitals in a square-planar ligand field.

5+5

5+5

5+5

Label each energy level. 5+5

6. (a) (i) Explain crystal field stabilization energy (CFSE). What are the factors that affect its magnitude?

(ii) Calculate CFSE and magnetic moments in case of

10+10

(b) (i) Write the general expressions for the filling of electrons in 4 f and 5 f block elements.

(ii) What do you understand by 'lanthanide contraction'? How does it affect the chemistry of 4/ and 5d block elements? 5+5

(c) (i) Write the IUPAC nomenclature of the following :

(1) K 3 [Fe(CN)5 ·NO)

(2) [Co(N02b · (NH3)3]

(ii) Why Ce3+ ion (4/1) is colourless, whereas Ti 3+ (3d1) solution is purple in

colour? 5+5

4

www.examrace.com

7. (a) (i) What are carbonyls? How are they formed? Show that the molecule Ni(C0)4 has a tetrahedral structure.

(ii) Write the structure ofFe2 (C0)9 . Show that each iron atom in the structure conforms to the 18e rule. 1 0+ 10

(b) Describe the structural features of 'ferredoxin' molecule. What is its role in photosynthesis? 10

(c) Draw labelled structures of all the possible isomers of dichloro-bis (ethylenediamine) cobalt(III) ion. Does a ·meso-form exist? Give reason to support your answer.

8. (a) (i) Discuss the solvent behaviour of liquid NH3 in respect of the following :

( 1) Alkali metals

(2) Urea

(3) BF3

(4) Amides (-NH2)

(5) Zn(NH2b +2NH4Cl

(ii) What is 'superadd'? Give two chemical properties to justify this

10

nomenclature. 1 0+ 10

(b) (i) Starting with [PtC14 ] 2-, prepare diamine dichloroplatinum(II). Name the

isomer formed.

(ii) Choose the relevant starting material and write all the steps to get the other geometrical isomer of the above product. 4+6

(c) (i) What do you understand by an 'oxidative addition' reaction?

(ii) How does it differ from ap. 'insertion reaction'? Give example in each case. 5+5

***

5 7BS-150

www.examrace.com

www.examrace.com

t •

CHEMISTRY Paper- II

I Time Allowed : Three Hours I Maximum Marks : 200 I

Question Paper Specific Instructions

Please read each of the following instructions carefully before attempting questions:

There are EIGHT questions in all, out of which FIVE are to be attempted. Questions no. 1 and 5 are compulsory. Out of the remaining SIX questions, THREE are to be attempted selecting at least ONE question from each of the two Sections A and B. Attempts of questions shall be counted in sequential order. Unless struck off, attempt of a question shall be counted even if attempted partly. Any page or portion of the page left blank in the Question-cum-Answer Booklet must be clearly struck off. All questions carry equal marks. The number of marks carried by a question I part is indicated against it. Answers must be written in ENGLISH only.

Unless otherwise mentioned, symbols and notations have their usual standard meanings. Assume suitable data, if necessary, and indicate the same clearly.

Neat sketches may be drawn, wherever required.

SECTION A

Ql. Answer the following : 5x8=40

(a) Classify the following compounds as aromatic, antiaromatic and non-aromatic. Explain your answer.

<±> s (f)

C) 0 Q (] s h-

A B c D

(b) Discuss the role of crossover experiments in determining the reaction mechanism.

1

5

5

www.examrace.com

(c) Quinuclidine reacts much faster with ethyl iodide than triethyl amine in

SN2 reaction. Explain. 5

(d) Arrange the following car boca tions in decreasing order of their stability.

Give reason in support of your answer. 5

A c D

(e) Arrange the following in decreasing order of basicity. Give explanation

to justify your ariswer. 5

(f)

0 N I

H

A B

0 N

c

Write the products formed in the following reactions:

(i) O<CH3

Br

(ii)

KOH,4m

EtOH, fl.

KOH

fl.

?

?

(g) Write the products formed in the following reaction sequence:

0

(i) MeAH A -----------+ B

PhLi

Dry ether

(h) Write the product and mechanism of the reaction :

OH OH

d b ?

5

5

5

t

•

www.examrace.com

• Q2. (a) (i) Write the outcome of the reaction and predict the reaction to SNl or SN2 in each case. 5

Br

HCOOH A

(- ) (+) HCOO Na B DMSO

(ii) Show the products of the following reactions :

(I) ?

(II) ?

(b) On attempted E2 reaction, A reacted much faster than B, while C reacted much faster than D. Explain with writing the product of the reaction in each case.

D D

A B c D , .

5

10

www.examrace.com

(c) (i) What product can one expect from the following reaction ? Depict

the stereochemical outcome at every step. 5

? NaOH

COOH (ii) What reagents are needed to bring the transformation ? 5

Q) OH

? ? cy OH

(d) Write a short note on aromatic character of sydnones. 10

Q3. (a) Write the structure of the product formed. 10

(i) ｾｉ＠AgN03

? 5

(ii) NaOH ? 5

(b) Complete the-following pericyclic reactions: 10

(i) ｾＰ＠OH

+'()_ ｾ Ｍ

? 5

OH

(ii) ? 5 ,,,,,,, H

t •

www.examrace.com

ｾ＠

• (c) (i) Explain correlation diagrams for electrocyclic interconversion of 1,3-butadiene and cyclobutene. 5

(ii) One of the cyclobutenes on heating reacts very fast while the other reacts at extremely slow rate. Explain. 5

.H H

A B

(d) Write the products in the following reactions:

(i)

(ii) p-ClC6H4NCO ＭＭＭＭＭＭＭｾ＿＠Et3N, Benzene, 25°C

(i) Zn, AcOH

(ii) .H 20 2

Q4. (a) Suggest a mechanism for the following reactions :

(i) 9? Me

CHO OH

Cl Cl (ii)

OH OH

10

? 5

5

10

5

5

www.examrace.com

(b) Claisen-ester condensation is possible with substrates of type A but not e

(c)

possible with type B. Explain by writing the mechanism. 10

0 0

ｒｾｏｅｴ＠ RYOEt R

A B

Discuss the mechanism of the reaction by writing the product.

ZnC12

HCl ?

10

(d) What are stabilized and unstabilized ylids? How does E-Z selectivity in Wittig reaction depend upon the nature ofylid? Explain. 10

www.examrace.com

t • SECTIONB

Q5. Attempt the following : 5x8=40

(a) Write the names of monomers of the following polymers and classify them as addition or condensation polymers : 5

(i) Teflon

(ii) Bakelite

(b) Name ｴｨｾ＠ products obtained on complete hydrolysis of DNA and give their structures.

(c) Write the structure of X, Y and Z.

((Z CH3

HI04 Base X Y ----+Z

(d) Formulate the product(s) and give the mechanism for the following reaction:

PhyPh

0

hv

(e) A compound contains two types of protons which exhibit signals at 139·2 Hz and 430·2 Hz downfield from TMS in a spectrometer operating at 60 MHz. What will be their relative position when measured on a

5

5

5

100 MHz instrument? 5

(f) Explain the following variations 1n /...max (in nm) of CH3Cl (173), CH3Br (204), CH3I (258). 5

(g) Why is a bathochromic shift observed with increasing conjugation in electronic spectra ? Explain.

(h) What is McLafferty rearrangement in Mass Spectrometry ? Mass spectrum of 1-phenyl butanone exhibits m/z (mass by charge) 105 as a base peak and m/z 120 as one of the major peaks. Explain.

7

5

5

www.examrace.com

Q6. (a) Calculate Mn and Mw for a polymer that consists of 10% by weight of a •

macromolecule of molecular weight 10,000 and 90% by weight of a

macromolecule with molecular weight i,OO,OOO. 10

(b) How will you determine the molecular weight of a polymer solution

using Ostwald viscometer ? 10

(c) State whether true or false. If false, give the correct statement. 2 x5=10

(i) Polyvinyl alcohol can be prepared by polymerization of vinyl

alcohol.

(ii) CH4 can be polymerized.

(iii) C2H2 and aniline cannot be polymerized.

(iv) Polymers have sharp melting point.

(v) Ziegler-Natta catalyst is used for the preparation of syndiotactic polymer.

(d) What is an oligopeptide? How is it different from a polypeptide? What

is the secondary structure of protein ? 10

Q7. (a) An organic liquid with molecular formula C6H100 gave the following

spectral data:

UV: vmax 230 run (e 12600i, 329 nm (e 41)

IR: vmax 2950- 2860 (m), 1695 (s), 1620 (m), 1460 (m) cm-1

NMR : () 1:9 (s, 3H), 2·1 (s, 6H), 6·15 (s, 1H)

Write the possible structure of compound with suitable justification.

Predict its 13C-NMR spectrum. 20

(b) How can the NMR spectrum distinguish between the isomers

p-xylene and ethyl benzene? Justify your answer.

(c) Give the ESR spectra of Naphthalene negative ion, Anthracene negative

10

ion and Triphenyl methyl radical. 10

www.examrace.com

ｾ＠

• Q8. (a) Complete the reactions and giVe appropriate mechanisms of the following : . 1 Ox3=30

0+ Ph\ H2S04 y (i)

X N02

10

OH

(ii) e) hv cb 10

H

hv (iii) N orrish Type II 10

0

(b) (i) Explain how many molecules of formaldehyde and formic acid are

formed in the reaction . 5

CHO I CHOH I CHOH I CHOH I CHOH I CH20H

(ii) Identify the X.

HI04

m-CPBA ＭＭＭｾｸ＠

X+Y

5

www.examrace.com

• ｾ＠ www.examrace.com