Practice problems on JEE Mains, JEE Mains 2021 Feb 26 Shift 1

Question 1

Which of the following vitamin is helpful in delaying the blood clotting?

Accepted Answer

Vitamin K

Answer

Vitamin B

Answer

Vitamin E

Answer

Vitamin C

Question 2

Find A, B and C in the following reactions :​NH3​+A+CO2​→(NH4​)2​CO3​(NH4​)2​CO3​+H2​O+B→NH4​HCO3​NH4​HCO3​+NaCl→NH4​Cl+C​

Accepted Answer

A−H2​O;B−CO2​;C−NaHCO3​

Answer

A−H2​O;B−O2​;C−Na2​CO3​

Answer

A−H2​O;B−O2​;C−NaHCO3​

Answer

A−O2​;B−CO2​;C−Na2​CO3​

Question 3

The intersection of three lines x−y=0 , x+2y=3 and 2x+y=6 is a:

Accepted Answer

Isosceles triangle

Answer

None of the above

Answer

Right angled triangle

Answer

Equilateral triangle

Question 4

Find the gravitational force of attraction between the ring and sphere as shown in the diagram, where the plane of the ring is perpendicular to the line joining the centres. If 8​R is the distance between the centres of a ring (of mass ' m ') and a sphere (mass ' M ') where both have equal radius 'R'

Accepted Answer

278​​⋅R2GmM​

Answer

38​1​⋅R2GMm​

Answer

98​​⋅RGmM​

Answer

322​​⋅R2GMm​

Question 5

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.Assertion A : An electron microscope can achieve better resolving power than an optical microscope.Reason R: The de Broglie's wavelength of the electrons emitted from an electron gun is much less than wavelength of visible light.In the light of the above statements, choose the correct answer from the options given below :

Accepted Answer

Both A and R are true and R is the correct explanation of A

Answer

A is false but R is true

Answer

Both A and R are true but R is NOT the correct explanation of A

Answer

A is true but R is false

Question 6

Consider the three planes​P1​:3x+15y+21z=9P2​:x−3y−z=5, and P3​:2x+10y+14z=5​ Then, which one of the following is true?

Accepted Answer

P1​ and P3​ are parallel

Answer

P2​ and P3​ are parallel

Answer

P1​ and P2​ are parallel

Answer

P1​ , P2​ and P3​ all are parallel

Question 7

The presence of ozone in troposphere :

Accepted Answer

Generates photochemical smog

Answer

Protects us from greenhouse effect

Answer

Protects us from the X-ray radiation

Answer

Protects us from the UV radiation

Question 8

Choose the most appropriate answer from the options given below :

Accepted Answer

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

Answer

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

Answer

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

Answer

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

Question 9

The orbital having two radial as well as two angular nodes is :

Accepted Answer

5 d

Answer

3p

Answer

4 d

Answer

4f

Question 10

A fair coin is tossed a fixed number of times. If the probability of getting 7 heads is equal to probability of getting 9 heads, then the probability of getting 2 heads is :

Accepted Answer

21315​

Answer

21215​

Answer

2815​

Answer

21415​

Question 11

A short straight object of height 100 cm lies before the central axis of a spherical mirror whose focal length has absolute value ∣f∣=40 cm . The image of object produced by the mirror is of height 25 cm and has the same orientation of the object. One may conclude from the information :

Accepted Answer

Image is virtual, opposite side of convex mirror

Answer

Image is virtual, opposite side of concave mirror

Answer

Image is real, same side of convex mirror

Answer

Image is real, same side of concave mirror

Question 12

The value of ∣∣​(a+1)(a+2)(a+3)​(a+2)(a+3)(a+4)​a+2a+3a+4​111​∣∣​ is :

Accepted Answer

−2

Answer

0

Answer

(a+2)(a+3)(a+4)

Answer

(a+1)(a+2)(a+3)

Question 13

An amine on reaction with benzenesulphonyl chloride produces a compound insoluble in alkaline solution. This amine can be prepared by ammonolysis of ethyl chloride. The correct structure of amine is :

Accepted Answer

CH3​CH2​CH2​ N−CH2​CH3​

Answer

CH3​CH2​NH2​

Answer

CH3​CH2​CH2​NHCH3​

Question 14

If (1,5,35),(7,5,5),(1,λ,7) and (2λ,1,2) are coplanar, then the sum of all possible values of λ is:

Accepted Answer

544​

Answer

−544​

Answer

539​

Answer

−539​

Question 15

The number of seven digit integers with sum of the digits equal to 10 and formed by using the digits 1,2 and 3 only is :

Accepted Answer

77

Answer

42

Answer

82

Answer

35

Question 16

Which of the following is 'a' FALSE statement?

Accepted Answer

Carius method is used for the estimation of nitrogen in an organic compound

Answer

Phosphoric acid produced on oxidation of phosphorus present in an organic compound is precipitated as Mg2​P2​O7​ by adding magnesia mixture

Answer

Kjeldahl's method is used for the estimation of nitrogen in an organic compound

Answer

Carius tube is used in the estimation of sulphur in an organic compound