Practice problems on JEE Mains, JEE Mains 2021 Mar 16 Shift 2

Question 1

Identify the elements X and Y using the ionisation energy values given below: Ionization energy (kJ/mol) XY​1st 495731​2nd 45631450​

Accepted Answer

X=Na;Y=Mg

Answer

X=Mg;Y=Na

Answer

X=F;Y=Mg

Answer

X=Mg;Y=F

Question 2

A bimetallic strip consists of metals A and B. It is mounted rigidly as shown. The metal A has higher coefficient of expansion compared to that of metal B . When bimetallic strip is placed in a cold bath, it will.

Accepted Answer

Bend towards the left

Answer

Bend towards the right

Answer

Not bend but shrink

Answer

Neither bend nor shrink

Question 3

The refractive index of a converging lens is 1.4. What will be the focal length of this lens if it is placed in a medium of same refractive index ? Assume the radii of curvature of the faces of lens are R1​ and R2​ respectively.

Accepted Answer

Infinite

Answer

Zero

Answer

1

Answer

R1​−R2​R1​R2​​

Question 4

Which of the following polymer is used in the manufacture of wool laminates?

Accepted Answer

Urea formaldehyde resin

Answer

cis-poly isoprene

Answer

Phenol and formaldehyde resin

Answer

Melamine formaldehyde resin

Question 5

Red light differs from blue light as they have:

Accepted Answer

Different frequencies and different wavelengths

Answer

Different frequencies and same wavelengths

Answer

Same frequencies and same wavelengths

Answer

Same frequencies and different wavelengths

Question 6

If the points of intersections of the ellipse 16x2​+b2y2​=1 and the circle x2+y2=4b,b>4 lie on the curve y2=3x2 , then b is equal to:

Accepted Answer

6

Answer

12

Answer

5

Answer

10

Question 7

The secondary structure of protein is stabilised by :

Accepted Answer

Hydrogen bonding

Answer

Peptide bond

Answer

Glycosidic bond

Answer

Van der Waals forces

Question 8

Which of the following is least basic?

Accepted Answer

(CH3​CO)2​NH¨

Answer

(CH3​CO)NHC¨2​H5​

Answer

(C2​H5​)3​N¨

Answer

(C2​H5​)N¨H

Question 9

The greenhouse gas/es is are:(A) Carbon dioxide(B) Oxygen(C) Water vapour(D) MethaneChoose the most appropriate answer from the options given below :

Accepted Answer

(A), (C) and (D) only

Answer

(A) and (C) only

Answer

(A) only

Answer

(A) and (B) only

Question 10

Let A denote the event that a 6 -digit integer formed by 0,1,2,3,4,5,6 without repetitions, be divisible by 3 . Then probability of event A is equal to :

Accepted Answer

94​

Answer

73​

Answer

2711​

Answer

569​

Question 11

If (x, y, z) be an arbitrary point lying on a plane P which passes through the points (42,0,0),(0,42,0) and (0,0,42) then the value of the expression3+(y−19)2(z−12)2x−11​+(x−11)2(z−12)2y−19​+(x−11)2(y−19)2z−12​+14(x−11)(y−19)(z−12)x+y+z​ is equal to:

Accepted Answer

3

Answer

−45

Answer

0

Answer

39

Question 12

If the foot of the perpendicular from point (4,3,8) on the line L1​:ℓx−a​=3y−2​=4z−b​ℓ=0 is (3,5,7), then the shortest distance between the line L1​ and line L2​:3x−2​=4y−4​=5z−5​ is equal to:

Accepted Answer

6​1​

Answer

32​​

Answer

21​

Answer

3​1​

Question 13

The INCORRECT statements below regarding colloidal solutions is :

Accepted Answer

An ordinary filter paper can stop the flow of colloidal particles.

Answer

The flocculating power of Al3+ is more than that of Na+.

Answer

A colloidal solution shows Brownian motion of colloidal particles.

Answer

A colloidal solution shows colligative properties.