IIT JAM CHEMISTRY 2021

SECTION – A
MULTIPLE CHOICE QUESTIONS (MCQ)

Q.2 For Na⁺, Mg²⁺, Al³⁺ and F⁻, the CORRECT order of ionic radii is
(A) Al³⁺ > Mg²⁺ > Na⁺ > F⁻
(B) Al³⁺ > Na⁺ > Mg²⁺ > F⁻
(C) F^- > Na⁺ > Mg²⁺ >Al³⁺
(C) Na⁺ > F^- > Mg²⁺ >Al³⁺

Q.3 Spin-only magnetic moments (in BM) of [NiCl₂(PPh₃)₂] and [Mn(NCS)₆] ⁴⁻ , respectively, are

(A) 0.00 and 5.92
(B) 2.83 and 1.89
(C) 0.00 and 1.89
(D) 2.83 and 5.92

Q.7 A compound shows ¹H NMR peaks at δ-values (in ppm) 7.31 (2H), 7.21 (2H), 4.5 (2H) and
2.3 (3H). The structure of the compound is

Q.9 A pure substance M has lesser density in solid state than in liquid state. The ΔS_fusion of M
is +25 J K⁻¹ mol⁻¹. The CORRECT representative Pressure-Temperature diagram for the fusion of M is

Q.11 Reaction of BCl₃ with NH₄Cl at 140 °C produces compound P. Further, P reacts with
NaBH4 to give a colorless liquid Q. The reaction of Q with H₂O at 100 C produces
compound R and a diatomic gas S. Among the following, the CORRECT statement is

A) P is B₃N₃H₆
(B) R is [B(OH)NH]₃
(C) Q is [BClNH]₃
(D) S is Cl₂

Q.12 The complex that does NOT obey the 18-electron rule is
(Given: Atomic numbers of Ti, Mn, Ta and Ir are 22, 25, 73 and 77, respectively)

(A) [(η⁵ -C₅H₅)Ti(CO)₄]⁻
(B) [Mn(SnPh₃)₂(CO)₄] ⁻
(C) [(η⁵-C₅H₅)Ir(CH2)(PM_e3)]
(D) [TaCl₃(PEt₃)₂(CHCMe₃)]

Q.13 Hybridization of the central atoms in I₃⁻, ClF₃ and SF₄, respectively, are

(A) sp³d, sp² and dsp²
(B) sp, sp³ d and dsp²
(C) sp³ d, sp³ d and sp³ d
(D) sp, sp² and sp³ d

Q.14 Reaction of [Ni(CN)₄] ²⁻ with metallic potassium in liquid ammonia at −33 °C yields complex E. The geometry and magnetic behavior of E, respectively, are

Q.17 According to the crystal field theory, d–d transition observed in [Ti(H₂O)₆] ³⁺ is

Q.25 Monochromatic X-rays having energy 2.8 x 10⁻¹⁵ J diffracted (first order) from (200)
plane of a cubic crystal at an angle 8.5º. The length of unit cell in Å of the crystal (rounded
off to one decimal place) is
(Given: Planck’s constant, h = 6.626 x 10⁻³⁴ J s; c = 3.0 x 10⁸ m s⁻¹)

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Q.29 The CORRECT statement regarding the molecules BF₃ and CH₄ is

(A) Both BF₃ and CH₄ are microwave active
(B) Both BF₃ and CH₄ are infrared active
(C) CH₄ is microwave active and infrared inactive
(D) BF₃ is microwave active and infrared active

SECTION - B
MULTIPLE SELECT QUESTIONS (MSQ)

Q.32 The complex(es) that show(s) Jahn-Teller distortion is (are)

(A) [Co(CN)₅(H₂O)]^3-
(B) [NiF₆]^2-
(C) [Mn(CNMe)₆]²⁺
(D) [Co(en)₂F₂]⁺

Q.36 The compound(s), which give(s) benzoic acid on oxidation with KMnO₄, is (are)

SECTION – C
NUMERICAL ANSWER TYPE (NAT)

Q.42 The total number of microstates possible for a d⁸ electronic configuration is ______.

Q.43 For the following fusion reaction,
4 ¹H -->⁴He + 2β⁺ + 2υ + γ the Q-value (energy of the reaction) in MeV (rounded off to one decimal place) is ______.
(Given: Mass of ¹H nucleus is 1.007825 u and mass of ⁴He nucleus is 4.002604 u)

Q.44 MgO crystallizes as rock salt structure with unit cell length 2.12 Å. From electrostatic
model, the calculated lattice energy in kJ mol⁻¹ (rounded off to the nearest integer) is ______.

(Given: NA = 6.022 x 1023 mol⁻¹; Madelung constant = 1.748;
ε₀ = 8.854 x 10⁻¹² J⁻¹ C² m⁻¹; charge of an electron = 1.602 x 10⁻¹⁹ C)

Q.45 Calcium crystallizes in fcc lattice of unit cell length 5.56 Å and density 1.4848 g cm⁻³. The
percentage of Schottky defects (rounded off to one decimal place) in the crystal is ______.
(Given: Atomic mass of Ca is 40 g mol⁻¹; NA = 6.022 x 1023 mol⁻¹)

Q.47 A buffer solution is prepared by mixing 0.3 M NH₃ and 0.1 M NH₄NO₃. If Kb of NH₃ is
1.6 x 10⁻⁵ at 25 ^oC, then the pH (rounded off to one decimal place) of the buffer solution at 25 ^oC is ______.

Q.48 The dissociation constant of a weak monoprotic acid is 1.6 x 10⁻⁵ and its molar conductance at infinite dilution is 360.5 x 10⁻⁴ mho m² mol⁻¹. For 0.01 M solution of this acid, the specific conductance is n x 10⁻² mho m⁻¹. The value of n (rounded off to two decimal places) is ______.

Q.49 Adsorption of a toxic gas on 1.0 g activated charcoal is 0.75 cm³ both at 2.5 atm, 140 K
and at 30.0 atm, 280 K. The isosteric enthalpy for adsorption of the gas in kJ mol⁻¹ (rounded off to two decimal places) is ______.
(Given: R = 8.314 J K⁻¹ mol⁻¹)

Q.50 If the root mean square speed of hydrogen gas at a particular temperature is 1900 m s⁻¹,
then the root mean square speed of nitrogen gas at the same temperature, in m s⁻¹ (rounded off to the nearest integer), is ______.
(Given: atomic mass of H is 1 g mol⁻¹; atomic mass of N is 14 g mol⁻¹)

Q. 51 – Q. 60 carry two marks each.
Q.51 If the crystal field splitting energy of [Co(NH₃)₄]²⁺ is 5900 cm⁻¹, then the magnitude of its
crystal field stabilization energy, in kJ mol⁻¹(rounded off to one decimal place), is ______

Q.52 A salt mixture (1.0 g) contains 25 wt% of MgSO₄ and 75 wt% of M₂SO₄. Aqueous solution of this salt mixture on treating with excess BaCl₂ solution results in the precipitation of 1.49 g of BaSO₄. The atomic mass of M in g mol⁻¹ (rounded off to two decimal places) is ______.
(Given: the atomic masses of Mg, S, O, Ba and Cl are 24.31, 32.06, 16.00, 137.33 and 35.45 g mol⁻¹, respectively)

Q.53 The intensity of a monochromatic visible light is reduced by 90% due to absorption on
passing through a 5.0 mM solution of a compound. If the path length is 4 cm, then the molar extinction coefficient of the compound in M⁻¹ cm⁻¹ is ______.

Q.54 The surface tension (γ) of a solution, prepared by mixing 0.02 mol of an organic acid in 1 L of pure water, is represented as γ* − γ = A log(1+Bc)
γ∗ is the surface tension of pure water, A = 0.03 N m^–1, B = 50 mol^–1 L and c is concentration in mol L^–1. The excess concentration of the organic acid at the surface of the liquid, determined by Gibbs adsorption equation at 300 K is n x 10sub>−6 mol m^–2. The value of n (rounded off to two decimal places) is ______.
(Given: R = 8.314 J K^–1 mol^–1)

Q.55 The separation of energy levels in the rotational spectrum of CO is 3.8626 cm−1. The bond
length (assume it does not change during rotation) of CO in Å (rounded off to two decimal
places) is ___________.
(Given: Planck’s constant h = 6.626 x 10⁻³⁴ J s; NA = 6.022 x 10²³ mol⁻¹; atomic mass of C is 12 g mol⁻¹ ; atomic mass of O is 16 g mol⁻¹ ; c = 3 x 10⁸ m s⁻¹)

Q.56 A dilute solution prepared by dissolving a nonvolatile solute in one liter water shows a depression in freezing point of 0.186 K. This solute neither dissociates nor associates in water. The boiling point of the solution in K (rounded off to three decimal places) is _________.
(Given: For pure water, boiling point = 373.15 K; cryoscopic constant = 1.86 K (mol kg⁻¹)⁻¹ ; ebullioscopic constant = 0.51 K (mol kg⁻¹)⁻¹)

Q.58 The mean ionic activity coefficient of 0.004 molal CaCl₂ in water at 298 K (rounded off to
three decimal places) is ______.
(Given: Debye-Hückel constant for an aqueous solution at 298 K is 0.509 kg^1/2 mol^-1/2)

Q.60 For the molecule,
CH3−CH=CH−CH(OH)−CH=CH−CH=C(CH3)2
the number of all possible stereoisomers is ______.