TIFR GS 2017 Question Paper Chemistry Y

CHM-Y
GS-2017 (Chemistry)
TATA INSTITUTE OF FUNDAMENTAL RESEARCH

Written Test in CHEMISTRY ‐ December 11, 2016
Duration : Three hours (3 hours)

Name : _______________________________________________ Ref. Code : ____________

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Page 1 of 18

SOME USEFUL DATA

Avogadro number = 6.02u1023 mol1 e = 1.6u1019 C
RT/F = 0.0257 V at 25qC h = 6.626u1034 J s
Faraday constant = 96500 C/mol c = 3u108 m s1
Boltzmann constant k = 1.38u1023 J K1 R = 8.314 J K1 mol1
Mass of an electron = 9.109u1031 kg

1) All natural amino acids, except one, react with cold nitrous acid and produce nitrogen gas.
Which one of the following is that odd amino acid?

A) Tryptophan

B) Glycine

C) Proline

D) Histidine

2) Predict the multiplicities for hydrogens on C1, C3, and C4 of butanone associated with the
spin-spin coupling in its 1H NMR spectrum.

A) H’s on C1: Singlet; H’s on C3: Doublet; H’s on C4: Triplet

B) H’s on C1: Singlet; H’s on C3: Triplet; H’s on C4: Quartet

C) H’s on C1: Singlet; H’s on C3: Quartet; H’s on C4: Triplet

D) H’s on C1: Triplet; H’s on C3: Doublet; H’s on C4, Triplet

3) If standard potential of the reaction 2H2O(l) = O2(g, 1bar) + 4H+(aq) + 4e- is E0 = -1.23 V.
At 25oC and pH =7, what is the oxidation potential of pure water according to this
reaction?

A) +0.410 V

B) -2.620 V

C) -0.817 V

D) -0.410 V
Page 2 of 18

4) An organic compound has the following spectroscopic properties: Mass Spectrometry:
m/z 102 (very small), 87 & 43 are the largest ions; 1H NMR: δ 1.4 & 3.9 ppm (both
singlets, intensity ratio 3:2); 13C NMR: δ 108, 64 & 25 ppm; Infrared spectroscopy:
several strong absorptions in the 1000 to 1300 cm-1 region. Which of the following is the
most likely formula of this compound?

A)

B)

C)

D)

5) Predict the relative rates for the following reductive elimination for X = H, Cl, CH3,
OCH3

A) Cl > H > CH3 > OCH3

B) H > Cl > OCH3 > CH3

C) OCH3 > CH3 > H > Cl

D) CH3 > H > Cl > OCH3

Page 3 of 18

6) A bio-conjugation reaction can be used to modify a specific residue on a protein to attach
therapeutics and diagnostic agents. Predict the major product of the following bio-
conjugation reaction with Fluorescein.

A)

B)

C)

D)

Page 4 of 18

7) For a hydrogen atom, which of the following orbital(s) have the lowest energy:

A) 4s

B) 4p

C) 4d

D) All of the above have same energy

8) An electron tunnels through a square barrier of width d and height h. If h is fixed and d is
is normally distributed, then the electron transfer probability distribution is:
A) a normal distribution

B) a delta function

C) a log normal distribution

D) a poisson distribution

9) In a cubic unit cell, identify the Miller plane (111)

A)

B)

C)

D) None of the above

Page 5 of 18

10)Zinc solid has hcp (hexagonal close packed) structure. In a unit cell of Zinc solid, the Zinc
atoms occupy

A) 74% of volume of unit cell.

B) 80% of volume of unit cell.

C) 68% of volume of unit cell.

D) 90% of volume of unit cell.

11) The acidity of molecules is usually measured by a parameter called the pKa. Metal ions
(Mn+) solubilized in water form solvated aqua complexes commonly denoted by
[M(H2O)m]n+ or Maqn+. It is known that the pKa of coordinated water in such metal-aqua
complexes will be different from that of bulk water. For the following set of metal-aqua
complexes: Caaq2+, Feaq2+, Mnaq2+, Feaq3+; arrange the complexes with decreasing value of
expected pKa of the coordinated water molecule:

A) Feaq2+ > Mnaq2+ > Caaq2+ > Feaq3+

B) Caaq2+ > Mnaq2+ > Feaq2+ > Feaq3+

C) Feaq2+ > Feaq3+ > Mnaq2+ > Caaq2+

D) Mnaq2+ > Caaq2+ > Feaq2+ > Feaq3+

12) Solid inorganic materials are commonly classified as conductors, semi-conductors or
insulators as determined by their bandgap. Carbon has many allotropes such as diamond,
graphite, carbon nanotubes and graphene with distinct bandgaps. Considering the
properties of diamond, what should be its bandgap:

A) 7.0 eV

B) 1.0 eV

C) 0.01 eV

D) 0 eV

Page 6 of 18

13) Predict the major product of the following hydroboration reaction:

A)

B)

C)

D)

14) Given an operator A and a set of vectors ࢄ which obey the following relationship

‫ ࢄܣ‬ൌ Oࢄ,

where O is the set of scalars. If A commutes with B and B ≠ A, which of the following is
correct:

A) X are eigenvectors of A only if the ߣ are all distinct (no two eigenvalues are equal)

B) X are eigenvectors of B

C) X are eigenvectors of B with set of eigenvalues ߣ

D) X need not be eigenvectors of A
Page 7 of 18

15) Given the molecular formula of the hexa-coordinated complexes

(I) Co Cl3 (NH3)6

(II) Co Cl3 (NH3)5

(III) Co Cl3 (NH3)4

If the number of coordinated NH3 molecules in (I), (II), and (III) respectively are 6, 5 and 4
then the oxidation state of Co in (I), (II) and (III) are respectively:

A) +6, +5, +4

B) +3, +2, +1

C) 0, +1, +2

D) +3, +3, +3

16) An aqueous solution contains 0.300 mole L1 of KH2PO4 and 0.015 mole L1 of K2HPO4.
Which of the following statements is true about this solution? [Data: For H3PO4, pK1 =
2.16, pK2 = 7.21, pK3 = 12.32]

A) It can act as a buffer solution around pH = 2

B) It can act as a buffer solution around pH = 12

C) Its pH will approximately equal to 6.9

D) Both B and C.

17) What is the value of the continued fraction given below?

ଶ଴଴଴
ͳ൅ మబబబ
ଶା మబబబ
మశ
మశ‫ڮ‬

A) 1999 B) ξʹͲͲͲ C) ξʹͲͲͳ D) None of them

Page 8 of 18

o

18) For angular momentum vector operator L , which of the following relation is true:

o o o2
A)
Lu L i! L
o o o
B) Lu L i! L
o o o
C) Lu L i! L
o o
D) Lu L 0

19) The complex showing a spin-only magnetic moment of 2.82 B.M. is

A) [Ni(CO)4]

B) [NiCl4]2-

C) [Ni(NH3)4]2+

D) [Ni(CN)4]2-

20) What are the products of the following reaction?

Page 9 of 18

21) Isotopic substitution is an often-used procedure in assigning vibrational spectroscopic
features but the difference in isotopic masses of the vibrating atoms has to be sufficiently
large to make the vibrational shift observable. In a double isotopic replacement
experiment, a proline with a 13C=18O carbonyl group is inserted in the middle of the
polypeptide using molecular recombinant techniques. Given that in the naturally found
proline the 12C=16O group exhibits a narrow vibrational feature at 1,711 cm−1, what is the
shift of the carbonyl stretching vibration for the 13C=18O proline isotopomer.

Assume:
a) The force constant for different isotopes can be considered identical.
b) The isotopic changes in the carbonyl group will have little effect on the vibrations of
other atoms in proline.

A) 80 cm-1

B) 165 cm-1

C) 85 cm-1

D) 42.5 cm-1

22) A compound with molecular formula C5H12O2, has strong infrared absorption at 3300 to
3400 cm-1. The 1H NMR spectrum showed three singlets at δ 0.90, δ 3.45 and δ 3.20
ppm; with relative areas 3:2:1. Addition of D2O to the sample eliminates the lower field
signal. The 13C NMR spectrum shows three signals all higher than δ 100 ppm. Which of
the following compounds best fits this data?

A) 1,5-pentanediol

B) 1,3-dimethoxypropane

C) 2,2-dimethyl-1,3-propanediol

D) 2,4-pentanediol

Page 10 of 18

23) The heat of formation ('Hf) for the reaction 2Cu(s) + O2(g) Æ 2CuO(s) is measured and
plotted as a function of temperature (T). Of the 4 possible graphs shown below, which
one would most likely represent the observed trend?

A) 1

B) 2

C) 3

D) 4

24) During isothermal expansion of an ideal gas which of the following happen:

(i) Temperature does not change

(ii) Process is spontaneous

(iii) The energy of the system does not change

(iv) Entropy increases

A) i and iii only

B) i, ii, and iv only

C) i, iii, and iv only

D) i, ii, iii and iv

Page 11 of 18

25)

NMR spectroscopy can be used to assay for drug binding to certain protein targets. One
of the primary objectives of any binding assay is the quantification of the free and the
bound forms of a drug molecule at a certain concentration of the protein target. Let us
assume that the fully bound drug exhibits a 1H chemical shift of δA while that of the free
form resonates at δB for the same proton (see figure above). If the exchange timescale
(i.e. proportional to kOFF as kON is diffusion limited) between the free form of the drug
and its bound form is in microseconds, which of the following statements cannot be true
assuming that the drug is only 50% bound with its protein target?

A) The NMR linewidth of the observed transition(s) will be different from the free form
of the drug.

B) There will be two resonances obtained in the NMR spectrum of the Protein-Drug
complex: one for the free form while other for the bound form.

C) We will see a single resonance at a position δeff which is in between δA and δB.

D) Varying the concentration of the drug molecule while observing the NMR signatures
will provide an estimate of the binding constant.

26) What is the value of ݅ ݈‫݃݋‬ଵ଴ ݅ ଶ , where ݅ ൌ ξെͳ ?

A) Real and positive number

B) Real and negative number

C) Complex number

D) Purely imaginary

Page 12 of 18

27) What are X and Y in the following reaction?

28) At 25 0C, if the pKa value for a weak acid is smaller than its aqueous solution pH by 2,
what is the fraction of the acid in dissociated form?

A) 1.10 %

B) 99.01 %

C) 0.99%

D) More information is needed

29) Cyclooctatetraene is

A) aromatic, because it is planar and it follows Hückel’s rule
B) antiaromatic, because it is not planar and it does not follow Hückel’s rule
C) antiaromatic, because it is planar and it does not follow Hückel’s rule
D) nonaromatic, because it is not planar and it does not follow Hückel’s rule

Page 13 of 18

30) In an experiment measuring the weight of the object, 100 repeats were performed by one
student. He found the mean weight of 332 grams with standard error of the mean as 5
grams. A lazier student only performs 10 measurements on the same object. Which of
the following values will her result be closest to?

A) 330 ± 50 grams

B) 400 ± 15 grams

C) 330 ± 15 grams

D) 330 ± 5 grams

31) The graph below plots the progress of a dimerization reaction involving species A. It
depicts a straight line with slope k (the rate constant). What is the value of the intercept,
c in the graph?

A) [A(0)]

B) [A(0)]2

C) [A(0)]-1

D) k x [A(0)]2

Page 14 of 18

32) Two compartments X and Y are separated by an impermeable partition P. In the
compartment X, the following reaction is going on in a solvent S, while the
compartment Y contains only the solvent S:

A2 + B2 l 2AB

Contents of both the compartments are continuously and vigorously stirred. After the
reaction in the compartment X has reached equilibrium, the concentrations of A2, B2
and AB are measured and the equilibrium constant calculated. Then the partition is
quickly removed. After waiting for a very long time, all the concentrations are
measured again, and the new value of the equilibrium calculated. What is the most
appropriate statement you can make about the result of this experiment? Assume that
the chemicals are behaving ideally and the temperature is kept constant.

X Y

P
A) The concentrations of all the chemicals and the equilibrium constant will be less
than their values before the partition was removed.

B) After removing the partition, the concentrations of A2 and B2 will increase, and that
of AB will decrease.

C) After removing the partition, the concentrations of A2 and B2 will decrease, and that
of AB will increase.

D) After removing the partition, the concentrations of all the chemicals will decrease.

33) Assume that the temperature (T) dependence of ∆G for a chemical reaction can be
represented by an equation of the form

∆G = x +›ܶ+zT2

What is the expression for the heat capacity change at constant pressure, 'Cp?

A) x/T

B) -y

C) -2zT

D) Insufficient information

Page 15 of 18

34) If the outer circle radius is ‘Z’, in the diagram given below, then what is the line segment
AB? The ratio of inner circles’ diameters is 2.

ସξଶ
A) ‫ݖ‬
ଷ

B) close to 2 Z

ξହ
C) ‫ݖ‬
ξଶ

ଶξହ
D) ‫ݖ‬
ଷ

35) A kid has been playing with an inflated balloon. Suddenly, a reaction happens inside the
balloon. This causes the inside surface of the balloon to become sticky, so that some of
the air molecules inside which collide against the surface get stuck to it. As a result,
immediately after the reaction, the balloon will

A) Inflate

B) Deflate

C) Remain unaltered

D) Will change its shape without changing its volume

36) The non-bonded interactions between two molecules consist of electrostatic (El) and van
der Waals (vdW) forces. Which of the following is a correct description of the distance
dependence intermolecular interactions between two molecules?
A) At large distances, El interactions decay faster than the vdW interactions
B) At large distances, vdW interactions decrease faster than the El interactions
C) Which force drops faster depends on the net charge of the molecules
D) Both interactions have same distance dependence
Page 16 of 18

37) “Doping” and “Alloying” are two common terms used to describe the presence of two
different elements in one material. Which one of the following statements is false?

A) Doping is the process of intentionally introducing impurities into an semiconductor in
order to change its electrical properties.

B) Doping means making one solid solution.

C) Alloying is a homogeneous mixture of two or more elements, at least one of which is
a metal.

D) In an alloy, the combined mixture has different properties from those of its component
elements.

38) What major products are obtained in the following Mitsunobu reaction?

A)

B)

C)

D)

Page 17 of 18

39) A particle in a 1-D box of length L has eigenstates ߰௡ ሺ‫ݔ‬ሻ with energies‫ܧ‬௡ . Consider two
initial states of the particle at time t = 0: case 1) Ȳሺ‫ݔ‬ǡ ‫ ݐ‬ൌ Ͳሻ ൌ ߰௡ (arbitrary n), and case
2) Ȳሺ‫ݔ‬ǡ ‫ ݐ‬ൌ Ͳሻ ൌ ߰௡ ൅ ߰௠ (arbitrary n and m; n ≠ m). The probability to find the particle
at a specific position within the box:

A) Varies with time for case 1 but not for case 2

B) Is time dependent for both cases

C) Is time independent for both cases

D) Varies with time for case 2 but not for case 1

40) In a rotational microwave spectrum of C12O16 lines were equally spaced by 3.863 cm-1.
In a rotational Raman spectrum of N2 (normal isotope) the lines were equally spaced by
8.04 cm-1. Assuming that the force constant for the two molecules is inversely
proportional to their bond lengths, the ratio of the vibrational frequency of CO to that of
N2 will be:

A) 0.8368

B) 0.9952

C) 1.0258

D) 1.2198

The following question does NOT carry any marks and is given to collect information only:

41) How much time did you take to complete this chemistry exam?

A) Less than 1 hour
B) Between 1 to 2 hours
C) Between 2 to 3 hours
D) Insufficient time was given

Page 18 of 18