Practice problems on JEE Mains, JEE Mains 2021 Aug 27 Shift 2

Question 1

The correct order of ionic radii for the ions, P3−,S2−,Ca2+,K+,Cl−is :

Accepted Answer

P3−>S2>Cl−>K+>Ca2+

Answer

P3−>S2>Cl−>Ca2+>K+

Answer

Cl−>S2>P3−>Ca2+>K+

Answer

K+>Ca2+>P3−>S2−>Cl−

Question 2

Potassium permanganate on heating at 513 K gives a product which is :

Accepted Answer

Paramagnetic and green

Answer

Paramagnetic and colourless

Answer

Diamagnetic and colourless

Answer

Diamagnetic and green

Question 3

Water drops are falling from a nozzle of a shower onto the floor from a height of 9.8 m. The drops fall at a regular interval of time. When the first drop strikes the floor, at that instant, the third drop begins to fall. Locate the position of second drop from the floor when the first drop strikes the floor.

Accepted Answer

7.35 m

Answer

2.94 m

Answer

4.18 m

Answer

2.45 m

Question 4

Match List-I with List-II :Choose the most appropriate answer from the options given below :

Accepted Answer

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

Answer

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

Answer

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

Answer

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

Question 5

Given below are two statements :Statement I : Ethyl pent-4-yn-oate on reaction with CH3MgBr gives a 3º-alcohol.Statement II : In this reaction one mole of ethyl pent-4-yn-oate utilizes two moles of CH3MgBr.In the light of the above statements, choose the most appropriate 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 false

Answer

Statement I is false but Statement II is true

Answer

Both Statement I and Statement II are true

Question 6

A mass of 50 kg is placed at the centre of a uniform spherical shell of mass 100 kg and radius 50 m. If the gravitational potential at a point, 25 m from the centre is V kg/m. The value of V is:

Accepted Answer

– 4 G

Answer

+ 2 G

Answer

– 20 G (3

Answer

– 60 G

Question 7

Two poles A B of length a metres and C D of length a+b(b=a) metres are erected at the same horizontal level with bases at B and D. If B D = x and tan∠ACB=21​, then :

Accepted Answer

x2−2ax+b(a+b)=0

Answer

x2+2(a+2b)x−b(a+b)=0

Answer

x2+2(a+2b)x+a(a+b)=0

Answer

x2−2ax+a(a+b)=0

Question 8

The boxes of masses 2 kg and 8 kg are connected by a massless string passing over smooth pulleys. Calculate the time taken by box of mass 8 kg to strike the ground starting from rest. (use g = 10 m/s2):

Accepted Answer

0.4 s

Answer

0.25 s

Answer

0.34 s

Answer

0.2 s

Question 9

Which one of the following reactions will not yield propionic acid ?

Accepted Answer

CH3​CH2​CH2​Br+Mg,CO2​ dry ether /H3​O+

Answer

CH3​CH2​CH3​+KMnO4​ (Heat), OH−/H3​O+

Answer

CH3​CH2​COCH3​+OH−/H3​O+

Answer

CH3​CH2​COOH3​+OI−/H3​O+

Question 10

Each of the persons A and B independently tosses three fair coins. The probability that both of them get the same number of heads is :

Accepted Answer

165​

Answer

85​

Answer

81​

Answer

1

Question 11

The oxide that gives H2​O2​ most readily on treatment with H2​O is :

Accepted Answer

Na2​O2​

Answer

BaO2​⋅8H2​O

Answer

SnO2​

Answer

PbO2​

Question 12

The compound/s which will show significant intermolecular H-bonding is/are :

Accepted Answer

(b) only

Answer

(a), (b) and (c)

Answer

(c) only

Answer

(a) and (b) only

Question 13

Choose the correct statement from the following :

Accepted Answer

Among the alkali metal halides, LiF is least soluble in water

Answer

LiF has least negative standard enthalpy of formation among alkali metal fluorides.

Answer

The standard enthalpy of formation for alkali metal bromides becomes less negative on descending the group

Answer

The low solubility of CsI in water is due to its high lattice enthalpy

Question 14

Which one of the following is formed (mainly) when red phosphorus is heated in a sealed tube at 803 K?

Accepted Answer

α - Black phosphorus

Answer

White phosphorus

Answer

Yellow phosphorus

Answer

β - Black phosphorus