TIFR GS 2026 Question Paper Chemistry

FOR TIFR GS EXAM PREPARATION

TIFR GS 2026
Question Paper ·
Chemistry
EXAM YEAR TYPE SUBJECT

TIFR GS 2026 Question Paper Chemistry

Notes · Sample Papers · Previous Year Papers · Mock Tests

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se 1. (Ph P) RhCl is a hydrogenation catalyst. Replacing alllathe PPh ligands with PEt
3 3
ag is the correct reason for the
diminishes the catalytic activity of the Rh compound. Following
3 3

loss of catalytic activity.
A) Replacing PPh3 with PEt3 makes a 18 electron compound
B) PEt3 is highly reactive and perform side reaction
C) Smaller cone angle of PEt3 allows stabilization and hence dissociation of Rh-PEt3 bond
becomes difficult
D) Replacing PPh3 with PEt3 makes a 16 electron compound

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a

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 1 of 40

2. The point group of Xe(O)F4 is
A) D4d
B) D4h
C) C4h
D) C4v

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se 3. Consider a small area element (with area = 𝑑𝑠) placed at g a
a ldistance from the origin (see
a
diagram below). Here, ̂ is a unit vector pointing in a direction normal to the area element 𝑑𝑠,
which is at an angle with the radial direction (denoted by ̂ ), and is the angle with the z-axis.
What is the correct expression of solid angle 𝑑 associated with this area element?

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s e l a
g l a ag
a

( )
A) 𝑑 =𝑑𝑠 2

( )
B) 𝑑 =𝑑𝑠 2

m
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( ) ( )
C) 𝑑 =𝑑𝑠 2

e m
s
( )
D) 𝑑 =𝑑𝑠
la
4 2

ag

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m .co s e m
s e g l a
g la a
a

m .
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s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 3 of 40

4. Which of the following are Hückel aromatic?

(a) (b) (c) (d)

A) (a), (c)
B) (b), (c)
C) (b), (d)
D) (a), (d)

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se g la involved in a laser. As a first
5. Consider an ensemble of atoms with two electronic energy levels
a
step of the lasing process, a population inversion is done. What can one say about the formal
absolute temperature of this population inverted ensemble state?

A) temperature cannot be defined
B) temperature is infinity
C) temperature is negative m
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D) temperature is 0
e m
e m l as
l as ag
ag

m
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s e
g la
a

m
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m .co s e m
s e g l a
g la a
a

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s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 5 of 40

6. Consider a vector ⃗ in a X-Y coordinate system. If the coordinate system is rotated by an angle
, , , ⃗ transform to ′, ′, ⃗′ (see diagram below). Which of the below expression describes the
correct relation among the horizontal and vertical components of ⃗ in the new and old coordinates?

′ 𝑠( ) 𝑠 ( )
A) [ ]=[ ][ ]
′ −𝑠 ( ) 𝑠( )
′ 𝑠( ) 𝑠 ( )
B) [ ]=[ ][ ]
′ 𝑠 ( ) 𝑠( )
′ − 𝑠( ) 𝑠 ( )
C) [ ]=[ ][ ]
′ 𝑠 ( ) 𝑠( )
𝑠( ) 𝑠 ( ) ′
D) [ ]=[ ][ ]
−𝑠 ( ) 𝑠( ) ′

Due to an ambiguity in the question, there is a possibility of multiple
interpretations. Consequently, both (a) and (d) are acceptable answers

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m
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se 7. Why do gold nanoparticles show melting points much lower thanla
a g bulk gold?

A) Their density is much higher than bulk gold
B) Surface atoms have lower coordination and weaker cohesive energy
C) Their bandgap becomes zero
D) They contain no free electrons

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a

m
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s e
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a

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m .co s e m
s e g l a
g la a
a

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 7 of 40

8. Determine the time required for visible light to pass vertically through a 100-μm-thick polymer
film when it enters at 45° and refracts at 30°?

A) 471 fs
B) 544 fs
C) 333 fs
D) 500 fs

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m .co s e m
se g l
9. A species A decays to form B according to a first-order reaction:a
→
a
Assume the initial concentration of A is [ ]0 and B is absent initially. (a) The time-dependent
growth of species B is proportional to what function of time? (b) How does the time-dependent ratio
of concentrations B/A vary as a function of time?

) ( )1- - ;( )
m
)( )1- - ;( ) -1
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)( ) ; ( ) - -1
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s e l a
a ag
)( ) -1 ( ) -
g l
a

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a

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s e g l a
g la a
a

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 9 of 40

10. Raman scattering is often seen overlapping with fluorescence emanating from the sample.
However fundamentally Raman process is different from fluorescence due to which of the
following:

A) Raman is a two-photon process while fluorescence is not
B) Raman scattering process has a slower timescale compared to fluorescence
C) Raman process is only about vibrational states while fluorescence deals with transitions
within electronic states
D) None of the above

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m
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se 11. Consider a quantum mechanical particle in one dimension withlaapotential of the following
a g
form:
( )=∞, <0
( )=+ sin ( ),0 ≤ ≤
( )=∞, >

Which of the following options correctly represents the first order correction to the ground state
m
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energy of this particle?
m
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A) +
4

s e l a
a ag
3

B) − gl
8
a 3
8
C) + 3

D) +

m
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s e
g la
a

m
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m .co s e m
s e g l a
g la a
a

m .
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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 11 of 40

12. Metallic silver (Ag) crystal space group is Fm3m. At 25 °C, lattice parameter is 4.0862 Å.
Which of the following descriptions are correct for Ag crystals?

A) BCC lattice, 2 atoms per unit cell, atomic radius is 2.0431 Å
B) BCC lattice, 4 atoms per unit cell, atomic radius is 2.0431 Å
C) FCC lattice, 4 atoms per unit cell, atomic radius is 1.44 Å
D) FCC lattice, 3 atoms per unit cell, atomic radius is 0.69 Å

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m
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se 13. For a van der Waals gas with parameters and , the critical g la
temperature is given by:
a
A)
27
8
B) 27

C)
8

D) 27 m
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m .co s e m
s e l a
g l a ag
a

m
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s e
g la
a

m
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m .co s e m
s e g l a
g la a
a

m .
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s em l a
g la ag
a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 13 of 40

14. What is the percent composition of a mixture of (S)-(+)-2-butanol, α= +13.52°, and (R)-(-)-2-
butanol, α = -13.52°, with a specific rotation α = +6.76°?

A) 75%(R) 25%(S)
B) 25%(R) 75%(S)
C) 50%(R) 50%(S)
D) 67%(R) 33%(S)

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se g la activation parameters ΔH‡
15. A ligand substitution reaction on an octahedral metal complex shows
= +60 kJ mol⁻¹ and ΔS‡ = −140 J mol⁻¹ K⁻¹. Which mechanismais most consistent and why?

A) Dissociative (D) — TS has increased disorder
B) Associative (A) — TS is highly ordered
C) Interchange dissociative (Id) — TS is modestly ordered
D) Radical — unrelated to ΔS‡

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 15 of 40

16. Consider a single-step hydrogen atom transfer reaction: - + → + - . If the rate constant
is at a temperature , then how is the rate constant, typically, going to change if the hydrogen
atom is replaced by a deuterium atom? ( is the rate constant for the case of deuterium transfer)

A) >
B) <
C) =
D) cannot be concluded

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se g la
17. If 2 fermions are placed in 6 spin-orbitals, how many unique arrangements are possible?
a
A) 12
B) 24
C) 15
D) 36

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 17 of 40

18. In the [Ti(H2O)6]3+ complex

A) All Ti-O bond distances are similar
B) Three of the Ti-O bond distances are shorter than the other three
C) Two of the Ti-O bond distances are longer than the other four
D) Two of the Ti-O bond distances are shorter than the other four

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se 19. Major product formed in the following transformation is:
g l a
a

m
m .co
m .co s e m
s e l a
g l a A) ag
a

B)

m
C)
m .co
s e
g la
a
D)

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m .co s e m
s e g l a
g la a
a

m .
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s em l a
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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 19 of 40

20. In the following pericyclic reaction the structure of allene formed and its configuration are

A)

B)

C)

D)

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se 21. The 31P NMR of phosphorus sesquisulfide, P4S3 reveals
g l a
a
A) a singlet
B) a singlet and a doublet
C) a doublet and a triplet
D) a doublet and a quartet

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s e g l a
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a

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 21 of 40

22. Fe(Cp)(CH3P)(Et)(CO) reacts with 13CO to form Fe(Cp)(CH3P)(COEt)(13CO). The product is
symmetry inverted, because the reaction proceeds via:

A) CO insertion step
B) Ethyl migration step
C) 13CO and CO exchange the position
D) None of the above

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se g
23. Consider a 1D wave-function given in the position space as la( ). What is the result of the
̂
̂
a
action of the operator exp (− ℏ ) on it, where is the momentum operator?

A) ( )
B) ( + )
C) ( − )
m
D) − ( )
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a

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m .co s e m
s e g l a
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a

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 23 of 40

24. A quantum system has energy levels 0, 2ε, and 4ε. At temperature T, what is the average energy
of the system?

A) ε(1 + 2e{-2ε/kT} + 4e{-4ε/kT}) / (1 + e{-2ε/kT} + e{-4ε/kT})
B) 2ε / (1 + e{-2ε/kT} + e{-4ε/kT})
C) ε / (1 + e{-2ε/kT} + e{-4ε/kT})
D) ε(2e{-2ε/kT} + 4e{-4ε/kT}) / (1 + e{-2ε/kT} + e{-4ε/kT})

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se g laJ/K. At what temperature does
25. For the reaction 2NO (g) → N O (g), ΔH = -57.2 kJ, ΔS = -175.8
2
the reaction become non-spontaneous?
2 4
a
A) T > 325.37 K
B) T < 325.37 K
C) T > 175.8 K
D) T < 175.8 K

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 25 of 40

26. The pKa1 of carbonic acid (H2CO3) is 6.3 while that of bicarbonate/carbonate equilibrium
(pKa2) shown below is 10.3.

Given the above data and pKw = 14, can one predict the pH of 0.01 M sodium bicarbonate solution
in water?

A) 7.5
B) 10.5
C) 8.3
D) 2.0

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m
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se g la molecule to be a harmonic
27. Suppose we consider the vibrational degree of freedom of a diatomic
oscillator. Consider a pth-order spectroscopic process which acouples with the vibrational dipole,
what would the selection rule be? (assume the vibrational dipole to be proportional to the position
of the reduced mass)

A) =±1
B) =±2
C) =±
D) − ≤ ≤ in steps of 2
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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 27 of 40

28. Arrange the following compounds in decreasing order of acidity.

A) I > II > III
B) II > I > III
C) III > I > II
D) II > III > I

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m
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se g laof metal-metal bonds and the
29. In the cluster [Co (CH)(CO) ] obeying 18 e rule, the number
3

bridging ligands respectively, are
9
a¯

A) 3 and 1 CO
B) 0 and 3 CO
C) 3 and 1 CH
D) 6 and 1 CH m
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a

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 29 of 40

30. Consider the reaction of [Co(NH3 )5 Cl]2+ with OH⁻ under strongly basic conditions. Which is
the most consistent pathway according to the experimental evidence?

A) Direct substitution of Cl⁻ by OH⁻ (outer‐sphere mechanism)
B) Deprotonation of an amine ligand to amido (–NH₂) followed by intramolecular substitution
C) Radical dissociation of Cl⁻ to form Co(III) with 5‐coordinated intermediate followed by an
OH⁻ attack
D) Concerted associative substitution via a seven‐coordinated intermediate

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m
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m .co s em
se g la being anharmonic, held at
31. Consider two 1D oscillators, the first being harmonic and the second
an inverse temperature =
1 a
. What can be said about the average kinetic energy of these two

oscillators respectively?

1 1
A) 2 , 2

m
1 3
B) ,
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2 2
m
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3 1
C)
2
,
2
m s e
s e l a
ag
3 3
D)
2
,
g l2a
a

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a

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g la a
a

m .
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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 31 of 40

32. In NiFe2O4, the coordination environment around nickel and iron are

A) All the nickel ions are in tetrahedral geometry, and all iron ions are in tetrahedral geometry
B) Half the nickel ions are in octahedral geometry the other half in tetrahedral geometry while
the iron ions are in octahedral geometry
C) Half the iron ions are in octahedral and the other half in tetrahedral geometry while the
nickel ions are in tetrahedral geometry
D) Half the iron ions are in octahedral and the other half in tetrahedral geometry while the
nickel ions are in octahedral geometry

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se 33. Consider the following graph:
g l a
a

m
m .co
m .co s e m
s e l a
g l a ag
a

Which of the following statements is correct?
1
A) ( )= and ( )= -| |
1+ 2
m
.co
1
B) ( )=- and ( )= -| |
m
1+ 2
C) ( )=-
1
and ( )= | |
s e
la
1+ 2
D) ( )=- -| | and ( )=
g
-1
1+ 2
a

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m .co s e m
s e g l a
g la a
a

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 33 of 40

34. If the partition function for a system is Z, which expression gives its average energy at
temperature T?

A) kB T Z
B) (∂Z/∂T)
1
C) -∂(ln Z)/∂β, where =
D)

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m
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m .co s em
se g latemperature (T), and pressure
35. Which Maxwell relation correctly links entropy (S), volume (V),
(P)?
a
A) (∂S/∂V)T = (∂P/∂T)V
B) (∂S/∂V)P = (∂T/∂P)S
C) (∂S/∂T)V = (∂V/∂P)S
D) (∂S/∂P)V = -(∂V/∂T)P

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s e g l a
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a

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 35 of 40

36. Which of the following is true when an isolated molecule gets excited to a charge neutral
excited state by visible light?

A) Reduced ionization potential
B) Increased ionization potential
C) No change in ionization potential
D) Zero ionization potential

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m
m .co

m .co s em
se g la
37. In a microcanonical ensemble, which pair of quantities is held constant?
a
A) Pressure and Temperature
B) Volume and Temperature
C) Volume and Energy
D) Temperature and Chemical Potential

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a

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a

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a

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 37 of 40

38. Consider two electrons in two different spatial orbitals whose spins are given as follows:

|↑↓⟩ − |↓↑⟩ |↑↓⟩ + |↓↑⟩
1 = ; 2 =
√2 √2

where ↑ represents the up spin and ↓ represents the down spin. What can we say about the spin
multiplicities of the two states?

A) Singlet; Triplet
B) Triplet; Singlet
C) Triplet; Triplet
D) Singlet; Singlet

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se g la
39. In the following reaction sequence involving platinum(II) complexes:
3
a ℎ3
[PtCl4 ]2− → [PtCl3 ( 3 )]
−
→ [PtCl2 ( 3 )( ℎ3 )]
Step 1 Step 2

Which of the following statements correctly predicts the major isomer and the reason for its
formation?

m
m
A) The trans isomer; because NH3 has a strong trans effect and directs substitution trans to
.co
itself .co s e m
s em l a
ag
B) The cis isomer; because chloride has a stronger trans effect than NH3, promoting

g la trans to itself
substitution
a
C) The trans isomer; because ℎ3 replaces the ligand cis to chloride
D) The cis isomer; because both NH3 and PPh3 have weak trans effects.

m
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s e
g la
a

m
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m .co s e m
s e g l a
g la a
a

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a For more Question Papers, Sample Papers, Notes & Syllabus visit Page 39 of 40

40. In ultrafast spectroscopy, a laser pulse of shorter duration has a larger spectral bandwidth. This
is because:

A) Short pulses have higher peak intensity, which results in a broad spectrum
B) The uncertainty principle dictates that the product of temporal and spectral widths must
remain approximately constant
C) Dispersion in optical materials compresses the pulse in time and broadens its frequency
content
D) Shorter pulses contain fewer optical cycles, reducing frequency spread

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