CHEMISTRY, PAPER–II

TIME ALLOWED: THREE HOURS MAXIMUM MARKS: 100

NOTE: (i) Attempt ONLY FIVE questions in all, including QUESTION NO.8, which is COMPULSORY.
All questions carry EQUAL marks.

(ii) Extra attempt of any question or any part of the attempted question will not be considered.
(iii) Candidate must draw two straight lines ( ) at the end to separate each
question attempted in Answer Books.


Q.1. (a) In what respect are sigma (s ) and pi (p ) bonds different from each other?
Explain. (7)
(b) What are H-bonds and how do they affect the properties of organic compounds?(6)
(c) Write an essay on hybridizatin and its significance in predicting the shape ofmolecules. (7)

Q.2. (a) Give a comparison of Valence Bond (VB) and Molecular Orbital (MO) theories
of bonding highlighting their important features. (7)
(b) What are aromatic compounds? What is the role of resonance energy towardsstability of the aromatic compounds? (7)
(c) Write an essay on isomerism. Elaborate its various types giving suitableexamples. (6)

Q.3. (a) How can temperature affect the rate of a reaction? Also make a diagram to
explain the energetics involved. (7)
(b) A ® product(s): is a second order reaction. Develop an integrated rate law for the
reaction and suggest a method to confirm that the reaction is second order.(7)
(c) Reaction of sodium ethoxide (Na+-OCH 2 CH 3 ) with bromomethane (CH3Br)
is about 10,000 times faster as compared to that with neopentyl bromide ((CH3)3
CCH2 Br). Explain with justification. (6)

Q.4. (a) Suggest one convenient method each for the preparation of RCHO
(an aldehyde) and R2CO (a Ketone). How to establish that the compound formed
is an aldehyde (or a Ketone) and not the Vice Versa? (7)
(b) Give a general explanation for the electrophilic substitution of benzene. Give
chemical equations showing all steps (with reaction conditions) for
bromination, nitration and alkylation of benzene. (7)
(c) Write an essay on the Grignard reagents. Give one example each in which
the Grignard reagent acts as base and as nucleophile. (6)

Q.5. (a) Differentiate between physical adsorption and chemisorption. How can the
nature of adsorption be established experimentally? (7)
(b) Explain the Langmuir adsorption isotherm and its applications. (6)
(c) Differentiate between molecularity and order of a reaction. Should they change if
the reaction conditions are changed? (7)

Q.6. (a) Suggest a method for the synthesis of benzene-diazonium chloride (BDC) from
nitrobenzene. Write down chemical equations for the reaction of BDC with7)
(a) KI (b) HBF4 (c) H3PO2 (d) C6H5NH2.
(b) Organic polymers have brought about a socio-economic revolution of present age.
Justify by referring to three important organic polymers. (7)
(c) Write an essay on Vitamins. Why are the Vitamin-A and C important? (6)

Q.7. (a) What are sulpha drugs? Give their general formula and methods of preparation.
Also write structures of two important sulpha drugs. (7)
(b) Write an essay on carbohydrates. What are special features of the
monosaccharides? (7)
(c) What are amides? What make them different in chemical reactivity compared to
aldehydes and Ketones? (6)

COMPULSORY QUESTION

Q.8. Write only the correct answer in the Answer Book. Do not reproduce the question.
(1) R - Product(s): is a 1st order reaction with respect to the concentration [R]. To
obtain a straight line with a slope equal to the rate constant k, which of thefollowings should be plotted against time?
(a) [R] (b) [R]2 (c) 1[R]
(d) ln[R] (e) None of these

(2) If the rate of a reaction does not change with time then the reaction should be:
(a) moderately slow (b) very fast (c) catalyzed
(d) zeroth order (e) None of these.

(3) If a chemical reaction reaches equilibrium state:
(a) its forward and backward rates are equal
(b) its overall free energy change becomes zero
(c) its equilibrium constant is the ratio of the two rate constants
(d) all of these (e) none of these

(4) PCl5(g) ® PCl3(g) +Cl2(g). The units of equilibrium constant, Kc for the reaction
is:
(a) L mol–1 (b) mol L –1 (c) mol –1 L –1
(d) mol –2 L–2 (e) None of these

(5) Energy of a typical H – bond ranges between:
(a) 2 to 4 kJmol –1 (b) 5 to 10 kJmol –1
(c) 15 to 30 kJmol –1 (d) 40 to 80 kJmol –1
(e) None of these

(6) Which of the pairs makes an “ideal mixture”:
(a) benzene-methanol (b) benzene-toluene
(c) ethanol-methanol (d) ethanol-water
(e) None of these

(7) Which of the following concentration units depends on temperature?
(a) molarity (b) molality
(c) mole fraction (d) weight to weight (W/W) %
(e) None of these

(8) A 0.4% (W/V) aqueous solution of NaOH is nearly:
(a) 1 M (b) 0.5 M (c) 0.1 M
(d) 0.01 M (e) None of these

(9) Which of the followings is correct for the ground state of O2 molecule?
(a) bond order two and no unpaired electron
(b) bond order two and one unpaired electron
(c) bond order two and two unpaired electron in the bonding orbital
(d) bond order two and two unpaired electrons in the anti-bonding orbital
(e) None of these

(10) Which one should give the simplest proton NMR spectrum?
(a) CH3CH2OH (b) CH3OH (c) CH3OCH3
(d) CH3CHO (e) all are equally complicated

(11) Which group has the highest stretching frequency of IR-region in the gas phase?
(a) º C -H (b) = C -H (c) – O – H
(d) – N – H (e) all are equal

(12) Which of the following should not be formed according to the bonding theories?
(a) H +
2 (b) H -
2 (c) He 2
(d) He2
+ (e) None of these

(13) There remains no liquid-vapour boundary at:
(a) boiling point (b) critical temperature
(c) triple point (d) azeotrope composition
(e) None of these

(14) For a catalyzed reaction as compared to the uncatalyzed one:
(a) heat of reaction is higher (b) heat of reaction is lower
(c) heat of reaction is same (d) activation energy is same
(e) All above are correct

(15) When two ideal gases at the same temperature are mixed together:
(a) there is a negative heat of mixing
(b) there is a positive heat of mixing
(c) both heat and entropy of mixing are positive
(d) entropy of mixing alone is positive
(e) All above are correct

(16) Which of the series is present in the ultraviolet region for the H – atom?
(a) Layman (b) Balmer (c) Paschen
(d) Pfund (e) None of these

(17) pH of 0.01 M HCl solution should be:
(a) 3 (b)2 (c)1.5
(d) 1 (e) None of these

(18) Which of the ions should exhibit highest electrical mobility in aqueous solution?
–
(a) Na+ (b) I (c) Cs+
(d) Cd++ (e) Li+

(19) H2 + Br2 ® 2HBr is a very famous gas phase reaction. The overall order of this
reaction is:
(a) two (b) one (c) half
(d) one half in the beginning (e) All above are correct

(20) Presence of a chiral center in molecules makes them:
(a) absorb uv–radiation (b) absorb plane polarized light
(c) rotate plane polarized light (d) emit IR–radiation
(e) None of these