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NEET Full Mock Test: Practice Test 4

Question paper with answer key. Selection Pro

Q1. A particle executes simple harmonic motion (SHM) with an amplitude $A$. At what displacement from the mean position is its kinetic energy equal to its potential energy?
  1. $\frac{A}{2}$
  2. $\frac{A}{\sqrt{2}}$
  3. $\frac{A}{4}$
  4. $\frac{\sqrt{3}A}{2}$

Answer: (B) $\frac{A}{\sqrt{2}}$

Kinetic Energy $KE = \frac{1}{2}m\omega^2(A^2 - x^2)$ and Potential Energy $PE = \frac{1}{2}m\omega^2 x^2$. Equating $KE = PE$ gives $A^2 - x^2 = x^2 \implies 2x^2 = A^2 \implies x = \frac{A}{\sqrt{2}}$.

Q2. The de Broglie wavelength of an electron accelerated through a potential difference of $V$ volts is approximately given by:
  1. $\frac{12.27}{\sqrt{V}}\text{ \AA}$
  2. $\frac{12.27}{V}\text{ \AA}$
  3. $\frac{\sqrt{V}}{12.27}\text{ \AA}$
  4. $12.27 \times \sqrt{V}\text{ \AA}$

Answer: (A) $\frac{12.27}{\sqrt{V}}\text{ \AA}$

De Broglie wavelength for an electron is $\lambda = \frac{h}{p} = \frac{h}{\sqrt{2meV}} = \frac{12.27}{\sqrt{V}}\text{ \AA}$.

Q3. Two resistors of resistances $R_1 = 6\ \Omega$ and $R_2 = 3\ \Omega$ are connected in parallel across a $6\text{ V}$ battery. The total current drawn from the battery is:
  1. $1\text{ A}$
  2. $2\text{ A}$
  3. $3\text{ A}$
  4. $0.67\text{ A}$

Answer: (C) $3\text{ A}$

Equivalent resistance $R_{eq} = \frac{R_1 R_2}{R_1 + R_2} = \frac{6 \times 3}{6 + 3} = 2\ \Omega$. Total current $I = \frac{V}{R_{eq}} = \frac{6}{2} = 3\text{ A}$.

Q4. The moment of inertia of a uniform solid sphere of mass $M$ and radius $R$ about its diameter is:
  1. $\frac{2}{5}MR^2$
  2. $\frac{2}{3}MR^2$
  3. $\frac{1}{2}MR^2$
  4. $\frac{7}{5}MR^2$

Answer: (A) $\frac{2}{5}MR^2$

The moment of inertia of a solid sphere about an axis passing through its center (diameter) is $I = \frac{2}{5}MR^2$.

Q5. A ray of light strikes a plane mirror at an angle of incidence of $30^\circ$. The angle of deviation produced by the mirror is:
  1. $30^\circ$
  2. $60^\circ$
  3. $120^\circ$
  4. $150^\circ$

Answer: (C) $120^\circ$

Angle of deviation for a plane mirror is given by $\delta = 180^\circ - 2i = 180^\circ - 2(30^\circ) = 120^\circ$.

Q6. A body of mass $5\text{ kg}$ is acted upon by two perpendicular forces $6\text{ N}$ and $8\text{ N}$. The magnitude of acceleration of the body is:
  1. $2\text{ m/s}^2$
  2. $2.8\text{ m/s}^2$
  3. $1.4\text{ m/s}^2$
  4. $10\text{ m/s}^2$

Answer: (A) $2\text{ m/s}^2$

Net force $F_{net} = \sqrt{6^2 + 8^2} = \sqrt{36 + 64} = 10\text{ N}$. Acceleration $a = \frac{F_{net}}{m} = \frac{10}{5} = 2\text{ m/s}^2$.

Q7. An ideal black body emits radiation at $27^\circ\text{C}$ at a rate $E$. If its temperature is raised to $327^\circ\text{C}$, the rate of radiation emission becomes:
  1. $2E$
  2. $4E$
  3. $8E$
  4. $16E$

Answer: (D) $16E$

According to Stefan-Boltzmann Law, $E \propto T^4$. $T_1 = 27+273 = 300\text{ K}$, $T_2 = 327+273 = 600\text{ K}$. $\frac{E_2}{E_1} = \left(\frac{600}{300}\right)^4 = 2^4 = 16 \implies E_2 = 16E$.

Q8. The work function of a metal surface is $2.0\text{ eV}$. The threshold frequency for photoelectric emission is approximately:
  1. $4.83 \times 10^{14}\text{ Hz}$
  2. $3.0 \times 10^{15}\text{ Hz}$
  3. $6.63 \times 10^{14}\text{ Hz}$
  4. $1.2 \times 10^{15}\text{ Hz}$

Answer: (A) $4.83 \times 10^{14}\text{ Hz}$

Work function $\Phi_0 = h \nu_0 \implies \nu_0 = \frac{\Phi_0}{h} = \frac{2.0 \times 1.6 \times 10^{-19}\text{ J}}{6.63 \times 10^{-34}\text{ J s}} \approx 4.83 \times 10^{14}\text{ Hz}$.

Q9. Which of the following elements has the highest electronegativity according to the Pauling scale?
  1. Oxygen
  2. Chlorine
  3. Fluorine
  4. Nitrogen

Answer: (C) Fluorine

Fluorine is the most electronegative element in the periodic table with a Pauling value of 4.0.

Q10. The geometry and hybridization of $\text{XeF}_4$ molecule are respectively:
  1. Tetrahedral, $sp^3$
  2. Square planar, $sp^3d^2$
  3. Octahedral, $sp^3d^2$
  4. Trigonal bipyramidal, $sp^3d$

Answer: (B) Square planar, $sp^3d^2$

$\text{XeF}_4$ has 4 bond pairs and 2 lone pairs on Xe (steric number = 6). Its steric hybridization is $sp^3d^2$, and shape/geometry of atoms is square planar.

Q11. Which of the following primary alcohols undergoes the fastest reaction with Lucas reagent (conc. $\text{HCl} + \text{ZnCl}_2$)?
  1. Methanol
  2. Ethanol
  3. Propan-1-ol
  4. 2-Methylpropan-2-ol

Answer: (D) 2-Methylpropan-2-ol

Lucas reagent reacts via $S_N1$ mechanism involving carbocation intermediate. 2-Methylpropan-2-ol is a tertiary alcohol and forms carbocation instantly, giving immediate turbidity.

Q12. The half-life period of a first-order reaction is $69.3\text{ minutes}$. What is the rate constant ($k$) of the reaction?
  1. $0.01\text{ min}^{-1}$
  2. $0.1\text{ min}^{-1}$
  3. $0.001\text{ min}^{-1}$
  4. $0.693\text{ min}^{-1}$

Answer: (A) $0.01\text{ min}^{-1}$

For a first-order reaction, $k = \frac{0.693}{t_{1/2}} = \frac{0.693}{69.3} = 0.01\text{ min}^{-1}$.

Q13. Aldol condensation is NOT given by which of the following compounds?
  1. Ethanal ($\text{CH}_3\text{CHO}$)
  2. Propanone ($\text{CH}_3\text{COCH}_3$)
  3. Benzaldehyde ($\text{C}_6\text{H}_5\text{CHO}$)
  4. Propanal ($\text{CH}_3\text{CH}_2\text{CHO}$)

Answer: (C) Benzaldehyde ($\text{C}_6\text{H}_5\text{CHO}$)

Aldol condensation requires at least one $\alpha$-hydrogen atom. Benzaldehyde lacks $\alpha$-hydrogens and hence undergoes Cannizzaro reaction instead.

Q14. Which transition metal complex shows optical isomerism?
  1. cis-$[\text{Co}(\text{en})_2\text{Cl}_2]^+$
  2. trans-$[\text{Co}(\text{en})_2\text{Cl}_2]^+$
  3. $[\text{Co}(\text{NH}_3)_4\text{Cl}_2]^+$
  4. $[\text{Ni}(\text{CN})_4]^{2-}$

Answer: (A) cis-$[\text{Co}(\text{en})_2\text{Cl}_2]^+$

cis-$[\text{Co}(\text{en})_2\text{Cl}_2]^+$ lacks a plane of symmetry and is non-superimposable on its mirror image, showing optical activity. The trans-isomer has a plane of symmetry.

Q15. According to Bronsted-Lowry concept, the conjugate base of $\text{HCO}_3^-$ is:
  1. $\text{H}_2\text{CO}_3$
  2. $\text{CO}_3^{2-}$
  3. $\text{OH}^-$
  4. $\text{CO}_2$

Answer: (B) $\text{CO}_3^{2-}$

Conjugate base is formed when an acid donates a proton ($H^+$). $\text{HCO}_3^- - \text{H}^+ = \text{CO}_3^{2-}$.

Q16. The basicity order of primary, secondary, and tertiary methylamines in aqueous solution is:
  1. $(\text{CH}_3)_2\text{NH} > \text{CH}_3\text{NH}_2 > (\text{CH}_3)_3\text{N} > \text{NH}_3$
  2. $(\text{CH}_3)_3\text{N} > (\text{CH}_3)_2\text{NH} > \text{CH}_3\text{NH}_2 > \text{NH}_3$
  3. $\text{CH}_3\text{NH}_2 > (\text{CH}_3)_2\text{NH} > (\text{CH}_3)_3\text{N} > \text{NH}_3$
  4. $(\text{CH}_3)_2\text{NH} > (\text{CH}_3)_3\text{N} > \text{CH}_3\text{NH}_2 > \text{NH}_3$

Answer: (A) $(\text{CH}_3)_2\text{NH} > \text{CH}_3\text{NH}_2 > (\text{CH}_3)_3\text{N} > \text{NH}_3$

In aqueous medium, due to inductive, steric, and solvation factors, the basicity order of methyl-substituted amines is $2^\circ > 1^\circ > 3^\circ > \text{NH}_3$ ($2130$).

Q17. In angiosperms, double fertilization involves:
  1. Fertilization of egg cell twice by two sperms
  2. Syngamy and Triple fusion
  3. Fusion of sperm with synergid and antipodal cell
  4. Fusion of two polar nuclei with one male gamete

Answer: (B) Syngamy and Triple fusion

Double fertilization comprises syngamy (fusion of one male gamete with egg) and triple fusion (fusion of second male gamete with two polar nuclei/diploid secondary nucleus).

Q18. Which stage of meiotic division is characterized by the alignment of bivalent chromosomes on the equatorial plate?
  1. Prophase I
  2. Metaphase I
  3. Anaphase I
  4. Metaphase II

Answer: (B) Metaphase I

During Metaphase I of meiosis, homologous chromosome pairs (bivalents) align on the equatorial plate.

Q19. Which nitrogen-fixing free-living aerobic bacterium is commonly present in soil?
  1. Rhizobium
  2. Azotobacter
  3. Anabaena
  4. Clostridium

Answer: (B) Azotobacter

Azotobacter and Beijerinckia are free-living aerobic nitrogen-fixing bacteria in soil.

Q20. Guttation in plants occurs due to the development of:
  1. Transpiration pull
  2. Root pressure
  3. Osmotic pressure
  4. Suction pressure

Answer: (B) Root pressure

Positive root pressure created during early morning/night pushes water out through hydathodes (guttation).

Q21. The functional unit of inheritance made up of DNA sequence is termed a:
  1. Cistron / Gene
  2. Codon
  3. Intron
  4. Exon

Answer: (A) Cistron / Gene

A gene (or cistron) is defined as a segment of DNA coding for a polypeptide or RNA molecule.

Q22. In C3 plants, the first stable carbon fixation product formed is:
  1. Oxaloacetic acid (OAA)
  2. 3-Phosphoglyceric acid (PGA)
  3. Phosphoenolpyruvate (PEP)
  4. Glucose

Answer: (B) 3-Phosphoglyceric acid (PGA)

In Calvin cycle (C3 pathway), carboxylation of RuBP yields two molecules of 3-Phosphoglyceric acid (3-PGA).

Q23. The interaction between orchid growing as an epiphyte on a mango branch is an example of:
  1. Mutualism
  2. Commensalism
  3. Parasitism
  4. Amensalism

Answer: (B) Commensalism

Commensalism is an interaction where one species benefits (orchid gets support) and the other is neither harmed nor benefited (mango tree).

Q24. Which plant hormone is widely used to induce rapid ripening of fruits?
  1. Ethylene
  2. Gibberellin
  3. Cytokinin
  4. Auxin

Answer: (A) Ethylene

Ethylene is a gaseous plant hormone that promotes fruit ripening and enhances respiration rate (climacteric rise).

Q25. Which of the following hormones is secreted by the corpus luteum after ovulation?
  1. Estrogen
  2. Progesterone
  3. LH
  4. FSH

Answer: (B) Progesterone

Ruptured Graafian follicle transforms into corpus luteum, which secretes large amounts of progesterone essential for maintaining endometrium.

Q26. The functional unit of the human kidney responsible for urine formation is:
  1. Neuron
  2. Nephron
  3. Alveolus
  4. Glomerulus

Answer: (B) Nephron

Nephron is the structural and functional filtration unit of the kidney.

Q27. Emphysema is a chronic respiratory disorder characterized by major damage to:
  1. Tracheal cartilages
  2. Bronchial lining
  3. Alveolar walls
  4. Diaphragm muscles

Answer: (C) Alveolar walls

Cigarette smoking leads to destruction of alveolar walls in emphysema, reducing respiratory surface area.

Q28. T-cells and B-cells involved in adaptive immune responses are types of:
  1. Monocytes
  2. Lymphocytes
  3. Neutrophils
  4. Eosinophils

Answer: (B) Lymphocytes

Lymphocytes are specialized agranulocytic white blood cells responsible for adaptive (acquired) immunity.

Q29. Which hormone regulates the 24-hour diurnal rhythm (sleep-wake cycle) of the human body?
  1. Melatonin
  2. Thymosin
  3. Oxytocin
  4. Cortisol

Answer: (A) Melatonin

Melatonin, secreted by the pineal gland, regulates sleep-wake cycles and diurnal body rhythms.

Q30. Which part of the alimentary canal in cockroaches serves for grinding food particles?
  1. Crop
  2. Gizzard (Proventriculus)
  3. Hepatic caeca
  4. Mesenteron

Answer: (B) Gizzard (Proventriculus)

The gizzard has an outer thick circular muscle layer and inner chitinous teeth used for grinding food particles.

Q31. The volume of air remaining in lungs even after a forcible maximal expiration is called:
  1. Tidal Volume
  2. Expiratory Reserve Volume
  3. Residual Volume
  4. Vital Capacity

Answer: (C) Residual Volume

Residual Volume (RV) is the volume of air left in lungs after forceful expiration (~1100 mL to 1200 mL).

Q32. Which contraceptive method acts by blocking gamete transport in human males?
  1. Tubectomy
  2. Vasectomy
  3. CuT insertion
  4. Oral contraceptive pills

Answer: (B) Vasectomy

Vasectomy is a surgical sterilization procedure in males where a small part of vas deferens is cut and tied to prevent sperm transport.