NEET 2020 Answer Key and Solutions

× 1.      A series LCR circuit is connected to an ac voltage source. When L is removed from the circuit, the phase difference between current and voltage is . If instead C is removed from the circuit, the phase difference is again between current and voltage. The power factor of the circuit is :

(1) 0.5

(2) 1.0

(3) –1.0

(4) Zero

Answer (2)

(1)

(2)

(3)

(4)

Answer (3)

(μ₀ = 4π × 10^–7 T m A^–1)

(1) 3.14 × 10^–4 T

(2) 6.28 × 10^–5 T

(3) 3.14 × 10^–5 T

(4) 6.28 × 10^–4 T

Answer (4)

(1)

(2) μA

(3)

(4)

Answer (2)

(1) 0.5 N/C

(2) 1 N/C

(3) 5 N/C

(4) zero

Answer (4)

× 6.     For which one of the following, Bohr model is not valid ?

(1) Singly ionised helium atom (He⁺)

(2) Deuteron atom

(3) Singly ionised neon atom (Ne⁺)

(4) Hydrogen atom

Answer (3)

× 7.     Light with an average flux of 20 W/cm² falls on a non-reflecting surface at normal incidence having surface area 20 cm². The energy received by the surface during time span of 1 minute is :

(1) 12 × 10³ J

(2) 24 × 10³ J

(3) 48 × 10³ J

(4) 10 × 10³ J

× 8.     An electron is accelerated from rest through a potential difference of V volt. If the de Broglie wavelength of the electron is 1.227 × 10^–2 nm, the potential difference is :

(1) 10² V

(2) 10³ V

(3) 10⁴ V

(4) 10 V

× 9.     A body weighs 72 N on the surface of the earth. What is the gravitational force on it, at a height equal to half the radius of the earth?

(1) 32 N

(2) 30 N

(3) 24 N

(4) 48 N

(1)

(2)

(3)

(4)

Answer (2)

× 11.      Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. What will be the photoelectric current if the frequency is halved and intensity is doubled?

(1) four times

(2) one-fourth

(3) zero

(4) doubled

Answer (3)

× 12.      A 40 μF capacitor is connected to a 200 V, 50 Hz ac supply. The rms value of the current in the circuit is, nearly :

(1) 2.05 A

(2) 2.5 A

(3) 25.1 A

(4) 1.7 A

Answer (2)

(1) 1.83 × 10^–7 rad

(2) 7.32 × 10^–7 rad

(3) 6.00 × 10^–7 rad

(4) 3.66 × 10^–7 rad

Answer (4)

(1) 340 m

(2) 320 m

(3) 300 m

(4) 360 m

Answer (3)

Its density is : (R = 8.3 J mol^–1 K^–1)

(1) 0.2 kg/m³

(2) 0.1 kg/m³

(3) 0.02 kg/m³

(4) 0.5 kg/m³

Answer (1)

× 16.      When a uranium isotope is bombarded with a neutron, it generates , three neutrons and :

(1)

(2)

(3)

(4)

Answer (4)

× 17.      The increase in the width of the depletion region in a p-n junction diode is due to :

(1) reverse bias only

(2) both forward bias and reverse bias

(3) increase in forward current

(4) forward bias only

Answer (1)

(1)

(2)

(3) zero

(4) π rad

Answer (4)

(μ₀ = 4π × 10^–7 T m A^–1)

(1) 8.0 × 10^–5 T m A^–1

(2) 2.4π × 10^–5 T m A^–1

(3) 2.4π × 10^–7 T m A^–1

(4) 2.4π × 10^–4 T m A^–1

Answer (4)

(1)

(2)

(3)

(4)

Answer (4)

(1) g/2

(2) g/5

(3) g/10

(4) g

Answer (2)

(1)

(2)

(3)

(4)

Answer (1)

(1) 200 V

(2) 400 V

(3) zero

(4) 50 V

Answer (1)

(1) [ML²T^–2]

(2) [ML⁰T^–2]

(3) [ML^–1 T^–2]

(4) [MLT^–2]

Answer (3)

× 25.      The energy required to break one bond in DNA is 10^–20 J. This value in eV is nearly

(1) 0.6

(2) 0.06

(3) 0.006

(4) 6

Answer (2)

× 26.      In a guitar, two strings A and B made of same material are slightly out of tune and produce beats of frequency 6 Hz. When tension in B is slightly decreased, the beat frequency increases to 7 Hz. If the frequency of A is 530 Hz, the original frequency of B will be

(1) 524 Hz

(2) 536 Hz

(3) 537 Hz

(4) 523 Hz

Answer (1)

The values of resistance and tolerance, respectively, are

(1) 47 kΩ, 10%

(2) 4.7 kΩ, 5%

(3) 470 Ω, 5%

(4) 470 kΩ, 5%

Answer (3)

(1) 30° < i_b < 45°

(2) 45° < i_b < 90°

(3) i_b = 90°

(4) 0° < i_b < 30°

Answer (2)

(∈₀ = 8.85 × 10^–12 C² N^–1 m^–2)

(1) 1.77 × 10^–12 C² N^–1 m^–2

(2) 0.44 × 10^–10 C² N^–1 m^–2

(3) 5.00 C² N^–1 m^–2

(4) 0.44 × 10^–13 C² N^–1 m^–2

Answer (2)

(1)

(2)

(3)

(4)

Answer (2)

(1) 1.0 × 10^–1 m

(2) 1.5 × 10^–1 m

(3) 1.5 × 10^–2 m

(4) 1.0 × 10^–2 m

Answer (1)

× 32.      For transistor action, which of the following statements is correct?

(1) Base, emitter and collector regions should have same size.

(2) Both emitter junction as well as the collector junction are forward biased.

(3) The base region must be very thin and lightly doped.

(4) Base, emitter and collector regions should have same doping concentrations.

Answer (3)

× 33.      The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is : ( c = speed of electromagnetic waves)

(1) 1 : 1

(2) 1 : c

(3) 1 : c²

(4) c : 1

Answer (1)

(1) 2.5 × 10⁶

(2) 2.5 × 10^–6

(3) 2.25 × 10^–15

(4) 2.25 × 10¹⁵

Answer (1)

(1) 1.28 × 10⁵ N/C

(2) 1.28 × 10⁶ N/C

(3) 1.28 × 10⁷ N/C

(4) 1.28 × 10⁴ N/C

Answer (1)

× 36.      Taking into account of the significant figures, what is the value of 9.99 m – 0.0099 m?

(1) 9.98 m

(2) 9.980 m

(3) 9.9 m

(4) 9.9801 m

Answer (1)

× 37.      In Young’s double slit experiment, if the separation between coherent sources is halved and the distance of the screen from the coherent sources is doubled, then the fringe width becomes :

(1) half

(2) four times

(3) one-fourth

(4) double

Answer (2)

× 38.      Two cylinders A and B of equal capacity are connected to each other via a stop cock. A contains an ideal gas at standard temperature and pressure. B is completely evacuated. The entire system is thermally insulated. The stop cock is suddenly opened. The process is :

(1) adiabatic

(2) isochoric

(3) isobaric

(4) isothermal

Answer (1)

(1) 4.5 × 10¹³ J

(2) 1.5 × 10¹³ J

(3) 0.5 × 10¹³ J

(4) 4.5 × 10¹⁶ J

Answer (1)

× 40.      A capillary tube of radius r is immersed in water and water rises in it to a height h. The mass of the water in the capillary is 5 g. Another capillary tube of radius 2r is immersed in water. The mass of water that will rise in this tube is :

(1) 5.0 g

(2) 10.0 g

(3) 20.0 g

(4) 2.5 g

Answer (2)

× 41.      A screw gauge has least count of 0.01 mm and there are 50 divisions in its circular scale.

The pitch of the screw gauge is :

(1) 0.25 mm

(2) 0.5 mm

(3) 1.0 mm

(4) 0.01 mm

Answer (2)

(1)

(2)

(3)

(4)

Answer (4)

(1)

(2)

(3)

(4)

Answer (1)

× 44.      The solids which have the negative temperature coefficient of resistance are:

(1) insulators only

(2) semiconductors only

(3) insulators and semiconductors

(4) metals

Answer (3)

× 45.      Two particles of mass 5 kg and 10 kg respectively are attached to the two ends of a rigid rod of length 1 m with negligible mass.
The centre of mass of the system from the 5 kg particle is nearly at a distance of :

(1) 50 cm

(2) 67 cm

(3) 80 cm

(4) 33 cm

Answer (2)

× 1.      Sucrose on hydrolysis gives:

(1) α-D-Glucose + β-D-Glucose

(2) α-D-Glucose + β-D-Fructose

(3) α-D-Fructose + β-D-Fructose

(4) β-D-Glucose + α-D-Fructose

Answer (2)

× 2.     Elimination reaction of 2-Bromo-pentane to form pent-2-ene is:

(a) β-Elimination reaction

(b) Follows Zaitsev rule

(c) Dehydrohalogenation reaction

(d) Dehydration reaction

(1) (a), (c), (d)

(2) (b), (c), (d)

(3) (a), (b), (d)

(4) (a), (b), (c)

Answer (4)

× 3.     The number of Faradays(F) required to produce 20 g of calcium from molten CaCl₂ (Atomic mass of Ca = 40 g mol^–1) is:

(1) 2

(2) 3

(3) 4

(4) 1

(1)

(2)

(3)

(4)

Answer (4)

(1) Only NaCl

(2) Only MgCl₂

(3) NaCl, MgCl₂ and CaCl₂

(4) Both MgCl₂ and CaCl₂

Answer (1)

(1) 2 × 10^–8 M

(2) 1 × 10^–13 M

(3) 1 × 10⁸ M

(4) 2 × 10^–13 M

Answer (4)

(1) Δ_rH > 0 and Δ_rS < 0

(2) Δ_rH < 0 and Δ_rS > 0

(3) Δ_rH < 0 and Δ_rS < 0

(4) Δ_rH > 0 and Δ_rS > 0

Answer (3)

(1)

(2)

(3)

(4)

Answer (4)

× 9.     The calculated spin only magnetic moment of Cr²⁺ ion is

(1) 4.90 BM

(2) 5.92 BM

(3) 2.84 BM

(4) 3.87 BM

Answer (1)

× 10.     Which of the following set of molecules will have zero dipole moment?

(1) Boron trifluoride, hydrogen fluoride, carbon dioxide, 1,3-dichlorobenzene

(2) Nitrogen trifluoride, beryllium difluoride, water, 1,3-dichlorobenzene

(3) Boron trifluoride, beryllium difluoride, carbon dioxide, 1,4-dichlorobenzene

(4) Ammonia, beryllium difluoride, water, 1,4-dichlorobenzene

Answer (3)

× 11.     The following metal ion activates many enzymes, participates in the oxidation of glucose to produce ATP and with Na, is responsible for the transmission of nerve signals.

(1) Copper

(2) Calcium

(3) Potassium

(4) Iron

(1)

(2)

(3)

(4)

Answer (2)

× 13.     The rate constant for a first order reaction is 4.606 × 10^–3 s^–1. The time required to reduce 2.0 g of the reactant to 0.2 g is :

(1) 200 s

(2) 500 s

(3) 1000 s

(4) 100 s

Answer (2)

× 14.     Reaction between acetone and methylmagnesium chloride followed by hydrolysis will give :

(1) Sec. butyl alcohol

(2) Tert. butyl alcohol

(3) Isobutyl alcohol

(4) Isopropyl alcohol

Answer (2)

× 15.     Which of the following is a natural polymer?

(1) poly (Butadiene-styrene)

(2) polybutadiene

(3) poly (Butadiene-acrylonitrile)

(4) cis-1,4-polyisoprene

Answer (4)

× 16.     Identify the correct statement from the following :

(a) CO₂(g) is used as refrigerant for ice-cream and frozen food.

(b) The structure of C₆₀ contains twelve six carbon rings and twenty five carbon rings.

(c) ZSM-5, a type of zeolite, is used to convert alcohols into gasoline.

(d) CO is colorless and odourless gas.

(1) (a) and (c) only

(2) (b) and (c) only

(3) (c) and (d) only

(4) (a), (b) and (c) only

Answer (3)

(1) q = 0, ΔT < 0 and w > 0

(2) q < 0, ΔT = 0 and w = 0

(3) q > 0, ΔT > 0 and w > 0

(4) q = 0, ΔT = 0 and w = 0

(1) H₂SO₄, sulphuric acid

(2) H₂S₂O₈, peroxodisulphuric acid

(3) H₂S₂O₇, pyrosulphuric acid

(4) H₂SO₃, sulphurous acid

Answer (2)

× 19.     Identify compound X in the following sequence of reactions

(1)

(2)

(3)

(4)

Answer (2)

× 20.     The number of protons, neutrons and electrons in respectively, are

(1) 104, 71 and 71

(2) 71, 71 and 104

(3) 175, 104 and 71

(4) 71, 104 and 71 Answer (4)

(1) The transition metals and their compounds are known for their catalytic activity due to their ability to adopt multiple oxidation states and to form complexes.

(2) Interstitial compounds are those that are formed when small atoms like H, C or N are trapped inside the crystal lattices of metals.

(3) The oxidation states of chromium in and are not the same.

(4) Cr²⁺ (d⁴) is a stronger reducing agent than Fe²⁺ (d⁶) in water.

Answer (3)

× 22.     Which of the following is a cationic detergent?

(1) Sodium stearate

(2) Cetyltrimethyl ammonium bromide

(3) Sodium dodecylbenzene sulphonate

(4) Sodium lauryl sulphate

Answer (2)

× 23.     The freezing point depression constant (K_f) of benzene is 5.12 K kg mol^–1. The freezing point depression for the solution of molality 0.078 m containing a non-electrolyte solute in benzene is (rounded off upto two decimal places) :

(1) 0.80 K

(2) 0.40 K

(3) 0.60 K

(4) 0.20 K

Answer (2)

× 24.      Identify the incorrect match.

(1) (b), (ii)

(2) (c), (iii)

(3) (d), (iv)

(4) (a), (i)

Answer (3)

× 25.     The mixture which shows positive deviation from Raoult’s law is

(1) Benzene + Toluene

(2) Acetone + Chloroform

(3) Chloroethane + Bromoethane

(4) Ethanol + Acetone

Answer (4)

× 26.     Match the following :

Which of the following is correct option?

Answer (1)

× 27.     Which one of the followings has maximum number of atoms ?

(1) 1 g of Mg(s) [Atomic mass of Mg = 24]

(2) 1 g of O₂(g) [Atomic mass of O = 16]

(3) 1 g of Li(s) [Atomic mass of Li = 7]

(4) 1 g of Ag(s) [Atomic mass of Ag = 108]

Answer (3)

× 28.     Reaction between benzaldehyde and acetophenone in presence of dilute NaOH is known as

(1) Cannizzaro’s reaction

(2) Cross Cannizzaro’s reaction

(3) Cross Aldol condensation

(4) Aldol condensation

Answer (3)

(1) + R effect of – CH₃ groups

(2) – R effect of – CH₃ groups

(3) Hyperconjugation

(4) – I effect of – CH₃ groups

Answer (3)

(1) It reduces oxygen carrying ability of blood.

(2) The carboxyhaemoglobin (haemoglobin bound to CO) is less stable than oxyhaemoglobin.

(3) It is produced due to incomplete combustion.

(4) It forms carboxyhaemoglobin

× 31.     Which of the following is a basic amino acid ?

(1) Alanine

(2) Tyrosine

(3) Lysine

(4) Serine

(1) [Cu(NH₃)₄]²⁺

(2) Cu(OH)₂

(3) CuCO₃·Cu(OH)₂

(4) CuSO₄

Answer (1)

× 33.     A mixture of N₂ and Ar gases in a cylinder contains 7 g of N₂ and 8 g of Ar. If the total pressure of the mixture of the gases in the cylinder is 27 bar, the partial pressure of N₂ is :

[Use atomic masses (in g mol^–1) : N = 14, Ar = 40]

(1) 12 bar

(2) 15 bar

(3) 18 bar

(4) 9 bar

Answer (2)

× 34.     Identify the correct statement from the following :

(1) Blister copper has blistered appearance due to evolution of CO₂.

(2) Vapour phase refining is carried out for Nickel by Van Arkel method.

(3) Pig iron can be moulded into a variety of shapes.

(4) Wrought iron is impure iron with 4% carbon.

Answer (3)

If the equilibrium constant (K_C) is 2 × 10¹³ at 300 K, the value of at the same temperature will be :

(1) 8.314 J mol^–1K^–1 × 300 K × ln(2 × 10¹³)

(2) 8.314 J mol^–1K^–1 × 300 K × ln(3 × 10¹³)

(3) –8.314 J mol^–1K^–1 × 300 K × ln(4 × 10¹³)

(4) –8.314 J mol^–1K^–1 × 300 K × ln(2 × 10¹³)

Answer (4)

× 36.     Identify a molecule which does not exist.

(1) Li₂

(2) C₂

(3) O₂

(4) He₂

Answer (4)

× 37.     An increase in the concentration of the reactants of a reaction leads to change in

(1) heat of reaction

(2) threshold energy

(3) collision frequency

(4) activation energy

× 38.     Which of the following alkane cannot be made in good yield by Wurtz reaction?

(1) 2,3-Dimethylbutane

(2) n-Heptane

(3) n-Butane

(4) n-Hexane

Answer (2)

(1)

(2)

(3)

(4)

Answer (4)

× 40.     On electrolysis of dil. sulphuric acid using Platinum (Pt) electrode, the product obtained at anode will be

(1) Oxygen gas

(2) H₂S gas

(3) SO₂ gas

(4) Hydrogen gas

Answer (1)

× 41.     What is the change in oxidation number of carbon in the following reaction?

CH₄(g) + 4Cl₂(g) → CCl₄(l) + 4HCl(g)

(1) 0 to + 4

(2) – 4 to + 4

(3) 0 to – 4

(4) + 4 to + 4

Answer (2)

(1)

(2)

(3)

(4)

Answer (4)

× 43.     Measuring Zeta potential is useful in determining which property of colloidal solution?

(1) Solubility

(2) Stability of the colloidal particles

(3) Size of the colloidal particles

(4) Viscosity

Answer (2)

× 44.     Paper chromatography is an example of

(1) Partition chromatography

(2) Thin layer chromatography

(3) Column chromatography

(4) Adsorption chromatography

Answer (1)

× 45.     Match the following and identify the correct option.

Answer (4)

× 1.     If the distance between two consecutive base pairs is 0.34 nm and the total number of base pairs of a DNA double helix in a typical mammalian cell is 6.6 × 10⁹ bp, then the length of the DNA is approximately

(1) 2.5 meters

(2) 2.2 meters

(3) 2.7 meters

(4) 2.0 meters

Answer (2)

(1) Platyhelminthes

(2) Aschelminthes

(3) Annelida

(4) Ctenophora

× 3.      Match the following columns and select the correct option.