JEE Main 2021 February 26 – Shift 2 Chemistry Question Paper with Solutions

SECTION A

Question 1. 2,4-DNP test can be used to identify

a. aldehyde
b. halogens
c. ether
d. amine

Answer: (a)

Question 2. Identify A in the following chemical reaction.

Answer: (c)

Question 3. The nature of charge on resulting colloidal particles when FeCl₃ is added to excess of hot water is:

a. positive
b. neutral
c. sometimes positive and sometimes negative
d. negative

Answer: (a)

If FeCl₃ is added to excess hot water, a positively charged sol of hydrated ferric oxide is formed due to the adsorption of Fe³⁺ ions.

Question 4. Match List-I with List-II

Choose the correct answer from the option given below:

a. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
b. (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
c. (a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)
d. (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)

Answer: (c)

Question 5. In molecule, the hybridization of carbon 1, 2, 3 and 4 respectively are:

a. sp², sp, sp², sp³
b. sp², sp², sp², sp³
c. sp², sp³, sp², sp³
d. sp³, sp, sp³, sp³

Answer: (a)

Question 6. Match List-I with List-II.

Choose the correct answer from the options given below:

a. (a)-(iii), (b)-(ii), (c)-(i)
b. (a)-(iii), (b)-(i), (c)-(ii)
c. (a)-(i), (b)-(iii), (c)-(ii)
d. (a)-(ii), (b)-(i), (c)-(iii)

Answer: (d)

Sucrose → a-D- Glucose and b-D- Fructose

Lactose → b-D- Galactose and b-D- Glucose

Maltose → a-D- Glucose and a-D- Glucose

Question 7. Which pair of oxides is acidic in nature?

a. N₂O, BaO
b. CaO, SiO₂
c. B₂O₃, CaO
d. B₂O₃, SiO₂

Answer: (d)

B₂O₃ and SiO₂ both are oxides of non-metal and hence are acidic in nature.

Question 8. Calgon is used for water treatment. Which of the following statements is NOT true about Calgon?

a. Calgon contains the 2^nd most abundant element by weight in the earth’s crust
b. It is also known as Graham’s salt.
c. It is a polymeric compound and is water-soluble.
d. It does not remove Ca²⁺ ion by precipitation.

Answer: (a)

Na₆(PO₃)₆ or Na₆P₆O₁₈

Order of abundance of element in earth crust is

O > Si > Al > Fe > Ca > Na > Mg > K

So, the second most abundant element in the earth’s crust is Si not Ca.

Question 9. Ceric ammonium nitrate and CHCl₃/alc. KOH are used for the identification of functional groups present in _________and________ respectively.

a. alcohol, amine
b. amine, alcohol
c. alcohol, phenol
d. amine, phenol

Answer: (a)

Alcohol gives a positive test with ceric ammonium nitrate and primary amines give carbonyl amine test with CHCl₃, KOH

Question 10. Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: In TlI₃, isomorphous to CsI₃, the metal is present in +1 oxidation
state.

Reason R: Tl metals has fourteen f electrons in its electronic configuration.

In the light of the above statements, choose the most appropriate Answer from the options given below:

a. Both A and R are correct and R is the correct explanation of A
b. A is not correct but R is correct
c. Both A and R are correct R is NOT the correct explanation of A
d. A is correct but R is not correct

Answer: (c)

TlI₃ is Tl⁺ I₃^–

CsI₃ is Cs⁺ I₃^–

Question 11. Thallium shows Tl⁺ state due to inert pair effect. The correct order of electron gain enthalpy is

a. S > Se > Te > O
b. O > S > Se > Te
c. S > O > Se > Te
d. Te > Se > S > O

Answer: (a)

Electron gain enthalpy of O is very low due to small size.

Question 12. Identify A in the given chemical reaction.

Answer: (a)

a.
_{(Internal aldol condensation)}

Question 13. Match List-I with List-II

Choose the correct answer from the options given below:

a. (a)-(i), (b)-(ii), (c)-(v), (d)-(iii)
b. (a)-(iii), (b)-(v), (c)-(i), (d)-(iv)
c. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
d. (a)-(iii), (b)-(i), (c)-(v), (d)

Answer: (b)

Siderite – FeCO₃

Calamine – ZnCO₃

Malachite – CuCO₃.Cu(OH)₂

Cryolite – Na₃AlF₆

Question 14. Identify A in the given reaction.

Answer: (b)

Question 15. Match List-I with List-II

Choose the correct answer from the option given below

a. (a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
b. (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
c. (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
d. (a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)

Answer: (b)

Sodium carbonate Na₂CO₃ and NaHCO₃

Titanium : Van arkel method

Ti + I₂ T1 → TiI_4(g)

TiI_4(g) T₂T₂>T₁ →Ti_{Refined titanium} +2I_2(G)

Chlorine: Decon’s process

HCl+O₂ CuCl₂ → H₂O+Cl₂

Sodium hydroxide: Caster-Kellner cell

Question 16. Match List-I with List-II.

Choose the correct answer from the options given below:

a. (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
b. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
c. (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
d. (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

Answer: (a)

Ne₂ BO = 0

N₂ BO = 3

F₂ BO = 1

O₂ BO = 2

As per the molecular orbital theory.

Question 17. Which of the following forms of hydrogen emits low energy b^– particles?

a. Proton H⁺
b. Deuterium

Question 18. Choose the correct order of the basic nature of the below given amines.

A. Phenyl methanamine

B. N, N-Dimethylaniline

C. N-Methyl aniline

D. Benzenamine

a. D > C > B > A
b. D > B > C > A
c. A > C > B > D
d. A > B > C > D

Answer: (d)

Question 19. Considering the given reaction, the major product among the following is:

Answer: (c)

Question 20. Seliwanoff test and Xanthoproteic test are used for the identification of __________ and ___________ respectively

a. ketoses, proteins
b. proteins, ketoses
c. aldoses, ketoses
d. ketoses, aldoses

Answer: (a)

Seliwanoff test and Xanthoproteic test are used for identification of ‘Ketoses’ and proteins respectively.

Question 2. The number of stereoisomers possible for [Co(ox)₂(Br)(NH₃)]^2- is ____________. [ox = oxalate]

Answer: 3

Total stereoisomer = 2 (OI) + 1 POE (pair of enantiomers) = 3

Question 3. The average S–F bond energy in kJ mol^–1 of SF₆ is __________. (Rounded off to the nearest integer)
[Given : The values of standard enthalpy of formation of SF₆(g), S(g) and F(g) are – 1100, 275 and 80 kJ mol^–1 respectively.]

Answer: 309

SF_6(g) → S_(g) + 6F_(g)

6 × E_S-F = 275 + 6×80 – (–1100) = 275 + 480 + 1100

6 × E_S-F = 1855

E_S-F = 1855/6 = 309.1667 = 309 kJ/mol

Question 4. E.m.f of the following cell at 298 K in V is x ×10^-2.

Zn|Zn²⁺ (0.1 M)||Ag⁺(0.01 M)| Ag

The value of x is _________. (Rounded off to the nearest integer)

Answer: 147

Zn(s)|Zn⁺²(0.1M)||Ag⁺(0.01M)|Ag(s)

( ) + 2 ? 2Ag(s) + Zn⁺²

E^o = 0.80 + 0.76 = 1.56; Q = {Zn²⁺ / (Ag²)²}

E = E^o – 0.059/n log(Q)

E = 1.56 – 0.059 / 2 log [0.1 / (0.01)²]

E = 1.56 – 0.059 / 2 log [(10)³]

E = 1.4715 = 147.15 × 10^-2 volt = x × 10^-2

X = 147.15 ? 147

Question 5. A ball weighing 10g is moving with a velocity of 90ms^-1. If the uncertainty in its velocity is 5%, then the uncertainty in its position is ________×10^-33m. (Rounded off to the nearest integer)

[Given: h = 6.63×10^-34 J s]

Answer: 1

m = 10 g = 10^-2 kg

v = 90 m/s

Δv = v × 5% = 90 × 5 / 100 = 4.5 m/s

Δx ≥ 1.17 × 10^-33 = x × 10^-33

x = 1.17?1

Question 6. In a mildly alkaline medium, thiosulphate ion is oxidized by to “A”. The oxidation state of sulphur in “A” is ________.

Answer: +6

S₂O^2-₃ + MnO^–₄  Alkaline Medium →A

A → SO^2-₄

Oxidation no. of ‘S’ = +6

Question 7. When 12.2 g of benzoic acid is dissolved in 100g of water, the freezing point of solution was found to be –0.93^oC (K_f (H₂O) = 1.86 K kg mol^-1). Then the number (n) of benzoic acid molecules associated (assuming 100% association) is_____________.

Answer: (2)

n PhCOOH (PhCOOH)_n

N = 1/x = i{As, α=1}

?T_f = i × k_f × m

0.93 = 1/n × 1.86 × 12.2 × 1000 / 122 × 100; n = 2

Question 8. If the activation energy of a reaction is 80.9 kJ mol^–1, the fraction of molecules at 700K, having enough energy to react to form products is e^–x. The value of x is ______. (Rounded off to the nearest integer)

[Use R = 8.31 JK^-1 mol^-1]

Answer: (14)

E_a = 80.9 kJ / mol

Fraction of molecules able to cross energy barrier = e – Ea / RT = e^-x

x = E_a / RT = 80.9 × 1000 / 8.31 × 700 = 13.91

x ? 14

Question 9. The pH of ammonium phosphate solution, if pk_a of phosphoric acid and pk_b of ammonium hydroxide are 5.23 and 4.75 respectively, is_____________.

Answer: 7

pH = pk_a + ½ {pk_w – pk_a – pk_b}

pH = 5.23 + ½ {14–5.23–4.75}

pH = 5.23 + ½ (4.02) = 7.24 = 7(Nearest integer)

Question 10. The number of octahedral voids per lattice site in a lattice is __________.

(Rounded off to the nearest integer)

Answer: 1

Assuming FCC

No of lattice sites = 6 face centre + 8 corner = 14

No. of octahedral voids = 13

Ratio = 13/14 = 0.92857 = 1 (nearest integer)

Video Solutions- February 2021 Question Papers