Practice problems on JEE Mains, JEE Mains 2021 Feb 25 Shift 2

Question 1

The major product of the following reaction is :

Accepted Answer

CH3​CH2​CH2​CH2​CHO

Answer

CH3​CH2​CH2​CHO

Answer

CH3​CH2​CH=CH−CHO

Question 2

The correct sequence of reagents used in the preparation of 4-bromo-2-nitroethyl benzene from benzene is :

Accepted Answer

CH3​COCl/AICl3​,Zn−Hg/HCl,Br2​/AIBr3​ ,HNO3​/H2​SO4​

Answer

HNO3​/H2​SO4​,Br2​/AICl3​,CH3​COCl/AICl3​,Zn−Hg/HCl

Answer

CH3​COCl/AICl3​,Br2​/AIBr3​,HNO3​/H2​SO4​, Zn/HCl

Answer

Br2​/AIBr3​,CH3​COCl/AICl3​,HNO3​/H2​SO4​ ,Zn/HCl

Question 3

In which of the following order the given complex ions are arranged correctly with respect to their decreasing spin only magnetic moment ?(i)[FeF6​]3−(ii)[Co(NH3​)6​]3+(iii)[NiCl4​]2−(iv)[Cu(NH3​)4​]2+

Accepted Answer

(i) > (iii) > (iv) > (ii)

Answer

(iii) > (iv) > (ii) > (i)

Answer

(ii) > (iii) > (i) > (iv)

Answer

(ii) > (i) > (iii) > (iv)

Question 4

Given below are two statements :Statement I: The identification of Ni2+ is carried out by Dimethylglyoxime in the presence of NH4​OH Statement II: The Dimethylglyoxime is a bidentate neutral ligand.In the light of the above statements, choose the correct answer from the options given below:

Accepted Answer

Statement I is true but Statement II is false

Answer

Both Statement I and Statement II are true

Answer

Both Statement I and Statement II are false

Answer

Statement I is false but Statement II is true

Question 5

Which among the following species has unequal bond lengths ?

Accepted Answer

SF4​

Answer

XeF4​

Answer

BF4−​

Answer

SiF4​

Question 6

If the curve x2 + 2﻿y2 = 2 intersects the line x + y = 1 at two points P and Q, then the angle subtended by the line segment PQ at the origin is :

Accepted Answer

2π​+tan−1(41​)

Answer

2π​−tan−1(41​)

Answer

2π​−tan−1(31​)

Answer

2π​+tan−1(31​)

Question 7

The truth table for the following logic circuit is :

Accepted Answer

A 0011​ B 0101​ Y 0110​​

Answer

A0011​B0101​Y1010​​

Answer

A 0011​ B 0101​ Y 1001​​

Answer

A0011​B0101​Y0101​​

Question 8

Which one of the following statements is FALSE for hydrophilic sols ?

Accepted Answer

Their viscosity is of the order of that of H2​O

Answer

They do not require electrolytes for stability

Answer

These sols are reversible in nature

Answer

The sols cannot be easily coagulated

Question 9

Given below are two statements :Statement I: α and β forms of sulphur can change reversibly between themselves with slow heating or slow cooling.Statement II: At room temperature the stable crystalline form of sulphur is monoclinic sulphur.In the light of the above statements, choose the correct answer from the options given below :

Accepted Answer

Statement I is true but Statement II is false.

Answer

Both Statement I and Statement II are true.

Answer

Both Statement I and Statement II are false.

Answer

Statement I is false but Statement II is true.

Question 10

Which of the following compound is added to the sodium extract before addition of silver nitrate for testing of halogens?

Accepted Answer

Nitric acid

Answer

Hydrochloric acid

Answer

Sodium hydroxide

Answer

Ammonia

Question 11

Let A be a set of all 4-digit natural numbers whose exactly one digit is 7. Then the probability that a randomly chosen element of A leaves remainder 2 when divided by 5 is :

Accepted Answer

29797​

Answer

92​

Answer

297122​

Answer

51​

Question 12

In a group of 400 people, 160 are smokers and non-vegetarian; 100 are smokers and vegetarian and the remaining 140 are nonsmokers and vegetarian. Their chances of getting a particular chest disorder are 35%, 20% and 10% respectively. A person is chosen from the group at random and is found to be suffering from the chest disorder. The probability that the selected person is a smoker and non-vegetarian is :

Accepted Answer

28/45

Answer

7/45

Answer

14/45

Answer

8/45

Question 13

Let x denote the total number of one-one functions from a set A with 3 elements to a set B with 5 elements and y denote the total number of one-one functions from the set A to the set A × B. Then :

Accepted Answer

2y = 91x

Answer

2y = 273x

Answer

y = 273x

Answer

y = 91x