NEET 2024 Previous Year Question Paper

Section A

1. Assertion (A): The kinetic energy of a body can never be negative. Reason (R): Kinetic energy equals ½mv², where m is positive and v² cannot be negative.

   1. Both A and R are true and R is the correct explanation of A
   2. Both A and R are true but R is not the correct explanation of A
   3. A is true but R is false
   4. A is false but R is true
   Answer and explanation

   Answer: A (Both A and R are true and R is the correct explanation of A)

   Both are true, and R explains A: with m > 0 and v² ≥ 0, ½mv² ≥ 0.

2. A ball is thrown vertically upward at 30 m/s (g = 10 m/s²). The maximum height reached is

   1. 30 m
   2. 60 m
   3. 90 m
   4. 45 m
   Answer and explanation

   Answer: D (45 m)

   H = u²/2g = 900/20 = 45 m.

3. The resistance of the filament of a bulb rated 60 W, 220 V is about

   1. 3.7 Ω
   2. 807 Ω
   3. 13 200 Ω
   4. 220 Ω
   Answer and explanation

   Answer: B (807 Ω)

   R = V²/P = 48 400/60 ≈ 806.7 Ω.

4. Nuclear radius R = R₀A^(1/3). The ratio of the radii of nuclei with mass numbers 27 and 64 is

   1. 9 : 16
   2. 3 : 4
   3. 27 : 64
   4. 1 : 1
   Answer and explanation

   Answer: B (3 : 4)

   R₁/R₂ = (27/64)^(1/3) = 3/4.

Section B

Attempt any 2 of these 3 questions (real paper: any 10 of 15).

5. A straight wire 2 m long carrying 3 A lies perpendicular to a uniform magnetic field of 0.5 T. The force on it is

   1. 0.75 N
   2. 12 N
   3. 1.5 N
   4. 3 N
   Answer and explanation

   Answer: D (3 N)

   F = BIL sin 90° = 0.5 × 3 × 2 = 3 N.

6. If the absolute temperature of an ideal gas is made four times, the rms speed of its molecules becomes

   1. the same
   2. twice
   3. four times
   4. sixteen times
   Answer and explanation

   Answer: B (twice)

   v_rms ∝ √T, so v becomes √4 = 2 times.

7. The critical angle for light going from glass of refractive index √2 into air is

   1. 90°
   2. 60°
   3. 45°
   4. 30°
   Answer and explanation

   Answer: C (45°)

   sin C = 1/n = 1/√2, so C = 45°.

Section A

8. Assertion (A): The electron gain enthalpy of fluorine is less negative than that of chlorine. Reason (R): Because fluorine is very small, an added electron feels strong repulsion from the electrons already in its compact 2p subshell.

   1. Both A and R are true and R is the correct explanation of A
   2. Both A and R are true but R is not the correct explanation of A
   3. A is true but R is false
   4. A is false but R is true
   Answer and explanation

   Answer: A (Both A and R are true and R is the correct explanation of A)

   Both are true (F ≈ −328 kJ/mol, Cl ≈ −349 kJ/mol), and the strong interelectronic repulsion in the small 2p subshell of F is the accepted explanation.

9. Which halide ion is the strongest reducing agent?

   1. Br⁻
   2. I⁻
   3. F⁻
   4. Cl⁻
   Answer and explanation

   Answer: B (I⁻)

   Reducing power of halide ions rises down the group (I⁻ > Br⁻ > Cl⁻ > F⁻) because I⁻ is large and loses its electron most easily.

10. The number of moles of O₂ needed for complete combustion of 2 mol of methane is

    1. 3
    2. 8
    3. 2
    4. 4
    Answer and explanation

    Answer: D (4)

    CH₄ + 2O₂ → CO₂ + 2H₂O, so 2 mol CH₄ needs 4 mol O₂.

11. The oxidation state of manganese in KMnO₄ is

    1. +6
    2. +4
    3. +7
    4. +2
    Answer and explanation

    Answer: C (+7)

    +1 + x + 4(−2) = 0, so x = +7.

Section B

Attempt any 2 of these 3 questions (real paper: any 10 of 15).

12. For a first-order reaction, the time for 90% completion is about how many times its half-life?

    1. 2
    2. 10
    3. 6.64
    4. 3.32
    Answer and explanation

    Answer: D (3.32)

    t90 = (2.303/k) log 10 = 2.303/k; t½ = 0.693/k. Ratio = 2.303/0.693 ≈ 3.32.

13. Which carbocation is the most stable?

    1. CH₃CH₂⁺
    2. (CH₃)₂CH⁺
    3. (CH₃)₃C⁺
    4. CH₃⁺
    Answer and explanation

    Answer: C ((CH₃)₃C⁺)

    The tertiary carbocation has the most hyperconjugation and +I stabilisation from three methyl groups.

14. In Lassaigne's test, nitrogen in an organic compound is shown by the formation of

    1. a black precipitate
    2. a violet colour
    3. Prussian blue
    4. a blood-red colour
    Answer and explanation

    Answer: C (Prussian blue)

    Sodium cyanide from fusion forms Na₄[Fe(CN)₆], which with Fe³⁺ gives Prussian blue (iron(III) hexacyanoferrate(II)).

Section A

15. Assertion (A): C₄ plants are more productive than C₃ plants at high temperature and light intensity. Reason (R): In C₄ plants, photorespiration is practically absent because CO₂ is concentrated around RuBisCO in bundle sheath cells.

    1. Both A and R are true and R is the correct explanation of A
    2. Both A and R are true but R is not the correct explanation of A
    3. A is true but R is false
    4. A is false but R is true
    Answer and explanation

    Answer: A (Both A and R are true and R is the correct explanation of A)

    Both are true and R explains A: concentrating CO₂ in bundle sheath cells stops RuBisCO acting as an oxygenase, so carbon is not lost to photorespiration.

16. Which pair of cell organelle and function is correctly matched?

    1. Centrosome – photosynthesis
    2. Golgi apparatus – packaging and secretion of materials
    3. Lysosome – protein synthesis
    4. Ribosome – lipid synthesis
    Answer and explanation

    Answer: B (Golgi apparatus – packaging and secretion of materials)

    The Golgi modifies, packages and dispatches materials. Ribosomes make protein, lysosomes digest, smooth ER makes lipids, and centrosomes organise spindle fibres.

17. The exine of the pollen grain is made of

    1. pectin
    2. sporopollenin
    3. cellulose
    4. lignin
    Answer and explanation

    Answer: B (sporopollenin)

    Sporopollenin is one of the most resistant organic materials known, which is why pollen is well preserved as fossils.

18. In eukaryotic mRNA processing, introns are removed by

    1. splicing
    2. capping
    3. translation
    4. tailing
    Answer and explanation

    Answer: A (splicing)

    During splicing, introns are cut out of hnRNA and exons are joined; capping and tailing modify the 5′ and 3′ ends.

Section B

Attempt any 2 of these 3 questions (real paper: any 10 of 15).

19. A double-stranded DNA sample has 20% adenine. Its cytosine content is

    1. 40%
    2. 60%
    3. 30%
    4. 20%
    Answer and explanation

    Answer: C (30%)

    A = T = 20%, so G + C = 60%, and G = C = 30%.

20. In the species–area relationship log S = log C + Z log A, the value of Z for most small areas typically lies between

    1. 0.6 and 1.2
    2. 1 and 2
    3. 0.1 and 0.2
    4. 0.01 and 0.02
    Answer and explanation

    Answer: C (0.1 and 0.2)

    Regression slopes (Z) are about 0.1–0.2 whatever the taxon or region; for very large areas such as whole continents they are steeper, about 0.6–1.2.

21. Which plant hormone delays leaf senescence?

    1. Abscisic acid
    2. Auxin only in roots
    3. Ethylene
    4. Cytokinin
    Answer and explanation

    Answer: D (Cytokinin)

    Cytokinins promote nutrient mobilisation and delay leaf senescence; ethylene and ABA promote it.

Section A

22. Assertion (A): Arteries have thick, elastic, muscular walls. Reason (R): Arteries carry blood away from the heart under high pressure.

    1. Both A and R are true and R is the correct explanation of A
    2. Both A and R are true but R is not the correct explanation of A
    3. A is true but R is false
    4. A is false but R is true
    Answer and explanation

    Answer: A (Both A and R are true and R is the correct explanation of A)

    Both are true and R explains A: the thick elastic tunica media withstands and smooths the high pressure surges from ventricular contraction.

23. Glucagon is secreted by which cells of the islets of Langerhans?

    1. acinar cells
    2. β-cells
    3. δ-cells
    4. α-cells
    Answer and explanation

    Answer: D (α-cells)

    α-cells secrete glucagon (raises blood glucose); β-cells secrete insulin.

24. Which of the following is an autoimmune disease?

    1. AIDS
    2. Malaria
    3. Rheumatoid arthritis
    4. Typhoid
    Answer and explanation

    Answer: C (Rheumatoid arthritis)

    In rheumatoid arthritis the immune system attacks the body's own joint tissues. Malaria and typhoid are infections; AIDS is an acquired immunodeficiency.

25. At rest, the axonal membrane is

    1. more permeable to K⁺ than to Na⁺
    2. impermeable to both ions
    3. equally permeable to Na⁺ and K⁺
    4. more permeable to Na⁺ than to K⁺
    Answer and explanation

    Answer: A (more permeable to K⁺ than to Na⁺)

    The resting membrane is relatively permeable to K⁺ and nearly impermeable to Na⁺, which, with the Na⁺/K⁺ pump, keeps the inside negative.

Section B

Attempt any 2 of these 3 questions (real paper: any 10 of 15).

26. Sickle-cell anaemia results from the substitution of

    1. valine by glutamic acid at position 6 of the α-chain
    2. lysine by valine at position 6 of the β-chain
    3. glutamic acid by valine at position 6 of the β-chain
    4. glutamic acid by lysine at position 6 of the α-chain
    Answer and explanation

    Answer: C (glutamic acid by valine at position 6 of the β-chain)

    A single-base change (GAG → GUG) replaces glutamic acid with valine at the sixth position of the β-globin chain.

27. Nourishment to developing sperm cells in the seminiferous tubules is provided by

    1. Sertoli cells
    2. Leydig cells
    3. spermatogonia
    4. interstitial macrophages
    Answer and explanation

    Answer: A (Sertoli cells)

    Sertoli (sustentacular) cells nourish germ cells; Leydig cells secrete testosterone.

28. Two parents, both carriers of an autosomal recessive disorder, have a child. The probability that the child is affected is

    1. 1/2
    2. 0
    3. 1/4
    4. 3/4
    Answer and explanation

    Answer: C (1/4)

    Aa × Aa gives AA : Aa : aa = 1 : 2 : 1, so the chance of aa is 1/4.