Practice problems on JEE Mains, JEE Mains 2021 Feb 24 Shift 2

Question 1

If one mole of an ideal gas at (P1​,V1​) is allowed to expand reversibly and isothermally (A to B) its pressure is reduced to one-half of the original pressure (see figure). This is followed by a constant volume cooling till its pressure is reduced to one-fourth of the initial value (B→C). Then it is restored to its initial state by a reversible adiabatic compression (C to A). The net work done by the gas is equal to :

Accepted Answer

RT(ln2−2(γ−1)1​)

Answer

−2(γ−1) RT ​

Answer

0

Answer

RTIn2

Question 2

Match List-I with List-II.Choose the correct answer from the options given below:

Accepted Answer

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

Answer

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

Answer

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

Answer

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

Question 3

The angle of elevation of a jet plane from a point A on the ground is 60°. After a flight of 20 seconds at the speed of 432 km/hour, the angle of elevation changes to 30°. If the jet plane is flying at a constant height, then its height is :

Accepted Answer

12003​ m

Answer

36003​ m

Answer

24003​ m

Answer

18003​m

Question 4

What is the correct order of the following elements with respect to their density?

Accepted Answer

Zn < Cr < Fe < Co < Cu

Answer

Cr < Zn < Co < Cu < Fe

Answer

Cr < Fe < Co < Cu < Zn

Answer

Zn < Cu < Co < Fe < Cr

Question 5

The area of the region : R={(x,y):5x2≤y≤2x2+9} is :

Accepted Answer

123​ square units

Answer

63​ square units

Answer

113​ square units

Answer

93​ square units

Question 6

Which of the following reagent is suitable for the preparation of the product in the above reaction?

Accepted Answer

NH2​−NH2​/C2​H5​OΘΘ​Na

Answer

Red P+Cl2​

Answer

Ni/H2​

Answer

NaBH4​

Question 7

What is the correct sequence of reagents used for converting nitrobenzene into :

Accepted Answer

Br2​/Fe,Sn/HCl,NaNO2​/HCl

Answer

NaNO2​,HCl,KBr,H+

Answer

Sn/HCl,Br2​,NaNO2​,NaBr

Answer

Sn/HCl,KBr,Br2​,H+

Question 8

Match List - I and List - II.Choose the correct answer from the options given below:

Accepted Answer

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

Answer

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

Answer

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

Answer

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

Question 9

The calculated magnetic moments (spin only value) for species [FeCl4​]2−,[Co(C2​O4​)3​]3−and MnO42−​ respectively are :

Accepted Answer

4.90, 0 and 1.73 BM

Answer

5.82, 0 and 0 BM

Answer

5.92, 4.90 and 0 BM

Answer

4.90, 0 and 2.83 BM

Question 10

Match List-I and List-II.

Accepted Answer

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

Answer

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

Answer

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

Answer

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

Question 11

A={x∈R:f Let f:R→R be defined as  Let A={x∈R:f is increasing }. Then A is equal to:

Accepted Answer

(−5,−4)∪(4,∞)

Answer

(−5,∞)

Answer

(−∞,−5)∪(4,∞)

Answer

(−∞,−5)∪(−4,∞)

Question 12

Zener breakdown occurs in a p-n junction having p and n both :

Accepted Answer

Heavily doped and have narrow depletion layer

Answer

Lightly doped and have narrow depletion layer

Answer

Heavily doped and have wide depletion layer

Answer

Lightly doped and have wide depletion layer

Question 13

For the system of linear equations :x−2y=1,x−y+kz=−2,ky+4z=6,k∈R (A) The system has unique solution if k=2,k=−2 (B) The system has unique solution if k = – 2(C) The system has unique solution if k = 2(D) The system has no solution if k = 2(E) The system has infinite number of solutions k = –2Which of the following statements are correct?

Accepted Answer

(A) and (D) only

Answer

(A) and (E) only

Answer

(B) and (E) only

Answer

(C) and (D) only