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NEET Full Mock Test: Practice Test 5

Question paper with answer key. Selection Pro

Q1. A capacitor of capacitance $C$ is charged to a potential difference $V$. It is then disconnected from the battery and connected across an uncharged capacitor of capacitance $2C$. The common potential after connection is:
  1. $\frac{V}{3}$
  2. $\frac{V}{2}$
  3. $\frac{2V}{3}$
  4. $3V$

Answer: (A) $\frac{V}{3}$

Common potential $V_{common} = \frac{C_1 V_1 + C_2 V_2}{C_1 + C_2} = \frac{C \cdot V + 2C \cdot 0}{C + 2C} = \frac{CV}{3C} = \frac{V}{3}$.

Q2. The dimensions of magnetic flux density (magnetic field $B$) are:
  1. $[M^1 L^0 T^{-2} A^{-1}]$
  2. $[M^1 L^1 T^{-2} A^{-1}]$
  3. $[M^1 L^2 T^{-2} A^{-1}]$
  4. $[M^0 L^1 T^{-2} A^{-1}]$

Answer: (A) $[M^1 L^0 T^{-2} A^{-1}]$

From force formula $F = q v B \implies B = \frac{F}{q v} = \frac{[M L T^{-2}]}{[A T][L T^{-1}]} = [M^1 L^0 T^{-2} A^{-1}]$.

Q3. A projectile is thrown with an initial velocity of $20\text{ m/s}$ at an angle of $30^\circ$ with the horizontal. Taking $g = 10\text{ m/s}^2$, the maximum height attained by the projectile is:
  1. $5\text{ m}$
  2. $10\text{ m}$
  3. $15\text{ m}$
  4. $20\text{ m}$

Answer: (A) $5\text{ m}$

Maximum height $H = \frac{u^2 \sin^2\theta}{2g} = \frac{20^2 \times \sin^2(30^\circ)}{2 \times 10} = \frac{400 \times (1/4)}{20} = 5\text{ m}$.

Q4. Which of the following electromagnetic waves has the highest frequency?
  1. Radio waves
  2. Microwaves
  3. Ultraviolet rays
  4. Gamma rays

Answer: (D) Gamma rays

Gamma rays have the shortest wavelength and highest frequency in the electromagnetic spectrum.

Q5. The escape velocity from Earth's surface is $11.2\text{ km/s}$. If a planet has double the radius and double the mass of Earth, the escape velocity from that planet will be:
  1. $11.2\text{ km/s}$
  2. $22.4\text{ km/s}$
  3. $5.6\text{ km/s}$
  4. $15.8\text{ km/s}$

Answer: (A) $11.2\text{ km/s}$

Escape velocity $v_e = \sqrt{\frac{2GM}{R}}$. If $M'=2M$ and $R'=2R$, then $v_e' = \sqrt{\frac{2G(2M)}{2R}} = \sqrt{\frac{2GM}{R}} = v_e = 11.2\text{ km/s}$.

Q6. An ideal heat engine operating between $127^\circ\text{C}$ and $27^\circ\text{C}$ has an efficiency of:
  1. $25\%$
  2. $50\%$
  3. $75\%$
  4. $20\%$

Answer: (A) $25\%$

Efficiency $\eta = 1 - \frac{T_2}{T_1} = 1 - \frac{27+273}{127+273} = 1 - \frac{300}{400} = 0.25 = 25\%$.

Q7. In a Zener diode used as a voltage regulator, the Zener breakdown occurs under:
  1. Forward bias with light doping
  2. Reverse bias with heavy doping
  3. Forward bias with heavy doping
  4. Reverse bias with light doping

Answer: (B) Reverse bias with heavy doping

Zener diodes are heavily doped p-n junctions designed to operate under reverse bias in the breakdown region.

Q8. The magnetic susceptibility ($ chi$) of a paramagnetic material is inversely proportional to absolute temperature $T$. This statement is known as:
  1. Curie's Law
  2. Lenz's Law
  3. Gauss's Law
  4. Ampere's Law

Answer: (A) Curie's Law

Curie's Law states that magnetic susceptibility of paramagnetic substances varies inversely with absolute temperature: $ chi = \frac{C}{T}$.

Q9. Which of the following organic compounds will give positive Fehling's test?
  1. Benzaldehyde
  2. Propanone
  3. Ethanal
  4. Acetophenone

Answer: (C) Ethanal

Aliphatic aldehydes like ethanal reduce Fehling's solution to give a red precipitate of $\text{Cu}_2\text{O}$. Aromatic aldehydes like benzaldehyde do not reduce Fehling's solution.

Q10. The oxidation number of phosphorus in orthophosphoric acid ($\text{H}_3\text{PO}_4$) is:
  1. $+3$
  2. $+5$
  3. $+1$
  4. $-3$

Answer: (B) $+5$

$3(+1) + x + 4(-2) = 0 \implies 3 + x - 8 = 0 \implies x = +5$.

Q11. Which of the following molecules has a non-zero dipole moment?
  1. $\text{CO}_2$
  2. $\text{BF}_3$
  3. $\text{CCl}_4$
  4. $\text{NH}_3$

Answer: (D) $\text{NH}_3$

$\text{NH}_3$ has a trigonal pyramidal shape with a lone pair on nitrogen, resulting in a net dipole moment ($ \mu \neq 0$). $\text{CO}_2$, $\text{BF}_3$, and $\text{CCl}_4$ are symmetrical ($ \mu = 0$).

Q12. Phenol reacts with dilute $\text{HNO}_3$ at room temperature to form:
  1. 2,4,6-trinitrophenol (Picric acid)
  2. ortho- and para-nitrophenols
  3. meta-nitrophenol only
  4. Nitrobenzene

Answer: (B) ortho- and para-nitrophenols

Dilute $\text{HNO}_3$ nitrates phenol to yield a mixture of o-nitrophenol and p-nitrophenol. Concentrated $\text{HNO}_3$ yields picric acid.

Q13. The bond order of $\text{O}_2^+$ ion according to Molecular Orbital Theory is:
  1. $2.0$
  2. $2.5$
  3. $1.5$
  4. $3.0$

Answer: (B) $2.5$

$\text{O}_2^+$ has 15 electrons. Bonding electrons $N_b = 10$, Antibonding $N_a = 5$. Bond order = $\frac{N_b - N_a}{2} = \frac{10 - 5}{2} = 2.5$.

Q14. Which among the following halogen acids is the strongest acid in aqueous solution?
  1. $\text{HF}$
  2. $\text{HCl}$
  3. $\text{HBr}$
  4. $\text{HI}$

Answer: (D) $\text{HI}$

Down the group, $H-X$ bond dissociation energy decreases ($H-I$ bond is weakest), making $\text{HI}$ release $H^+$ ions most easily.

Q15. The half-life of a zero-order reaction is directly proportional to:
  1. Initial concentration of reactant $[A]_0$
  2. Square of initial concentration $[A]_0^2$
  3. Inverse of initial concentration $\frac{1}{[A]_0}$
  4. Temperature only

Answer: (A) Initial concentration of reactant $[A]_0$

For zero-order reaction, $t_{1/2} = \frac{[A]_0}{2k}$, which shows $t_{1/2} \propto [A]_0$.

Q16. Which vitamin deficiency causes Pernicious Anemia?
  1. Vitamin B1
  2. Vitamin B6
  3. Vitamin B12
  4. Vitamin C

Answer: (C) Vitamin B12

Deficiency of Vitamin B12 (Cyanocobalamin) impairs RBC maturation leading to Pernicious Anemia.

Q17. Which of the following plant tissues consists of dead cells at maturity?
  1. Parenchyma
  2. Collenchyma
  3. Sclerenchyma
  4. Companion cells

Answer: (C) Sclerenchyma

Sclerenchyma cells possess heavily lignified cell walls and lose protoplasm at maturity, becoming dead cells.

Q18. The enzyme responsible for primary carbon fixation in C3 cycle (Calvin Cycle) is:
  1. PEP Carboxylase
  2. RuBisCO
  3. ATP Synthase
  4. Pyruvate Dehydrogenase

Answer: (B) RuBisCO

RuBisCO (Ribulose-1,5-bisphosphate carboxylase-oxygenase) catalyzes $\text{CO}_2$ fixation in the Calvin cycle.

Q19. In DNA structure, two polynucleotide strands are held together by:
  1. Phosphodiester bonds
  2. Glycosidic bonds
  3. Hydrogen bonds
  4. Peptide bonds

Answer: (C) Hydrogen bonds

Hydrogen bonds between complementary nitrogenous bases (A=T and Cā‰”G) hold the double helix strands together.

Q20. Which of the following is an example of non-vascular embryophyte?
  1. Algae
  2. Bryophytes
  3. Pteridophytes
  4. Gymnosperms

Answer: (B) Bryophytes

Bryophytes form embryos during development but lack vascular tissues (xylem and phloem).

Q21. The technique used to separate fragments of DNA based on their size is:
  1. Polymerase Chain Reaction (PCR)
  2. Agarose Gel Electrophoresis
  3. Northern Blotting
  4. Centrifugation

Answer: (B) Agarose Gel Electrophoresis

Agarose gel electrophoresis separates negatively charged DNA fragments toward anode based on molecular size.

Q22. In a mendelian dihybrid cross ($AaBb \times AaBb$), the phenotypic ratio in $F_2$ generation is:
  1. $3:1$
  2. $1:2:1$
  3. $9:3:3:1$
  4. $9:7$

Answer: (C) $9:3:3:1$

The classic mendelian dihybrid phenotypic ratio across independently assorting traits is $9:3:3:1$.

Q23. Water potential of pure water at standard temperature and pressure is equal to:
  1. Zero
  2. 100
  3. 10
  4. $-10$

Answer: (A) Zero

By convention, pure water at standard temperature and atmospheric pressure has a water potential ($\Psi_w$) of zero.

Q24. Which cell organelle is rich in hydrolytic enzymes functioning at acidic pH?
  1. Lysosome
  2. Peroxisome
  3. Glyoxysome
  4. Vacuole

Answer: (A) Lysosome

Lysosomes contain acid hydrolases (lipases, proteases, carbohydrases) optimal at acidic pH (~5.0).

Q25. The specialized junction that facilitates rapid transfer of ions and small molecules between adjacent cardiac muscle cells is:
  1. Tight junction
  2. Adhering junction
  3. Gap junction
  4. Desmosome

Answer: (C) Gap junction

Gap junctions (intercalated discs) allow rapid electrical communication and ion passage between cardiac cells.

Q26. Which hormone is responsible for ejection of milk from mammary glands during lactation?
  1. Prolactin
  2. Oxytocin
  3. Estrogen
  4. Progesterone

Answer: (B) Oxytocin

Oxytocin causes contraction of myoepithelial cells in mammary glands, stimulating milk let-down/ejection.

Q27. In human nephron, maximum reabsorption of water and essential nutrients takes place in:
  1. Proximal Convoluted Tubule (PCT)
  2. Henle's Loop
  3. Distal Convoluted Tubule (DCT)
  4. Collecting Duct

Answer: (A) Proximal Convoluted Tubule (PCT)

Nearly 70ā€“80% of electrolytes and water and virtually all essential nutrients are reabsorbed in PCT.

Q28. Antibodies present in human colostrum that provide natural passive immunity to infants belong to class:
  1. IgG
  2. IgA
  3. IgM
  4. IgE

Answer: (B) IgA

Colostrum is rich in IgA antibodies which protect the newborn's gastrointestinal tract.

Q29. Which part of human ear contains sensory hair cells responsible for hearing?
  1. Organ of Corti
  2. Macula
  3. Crista ampullaris
  4. Eustachian tube

Answer: (A) Organ of Corti

Organ of Corti, located on basilar membrane inside cochlea, contains hair cells functioning as auditory receptors.

Q30. During muscle contraction, which band/zone in the sarcomere shortens and disappears?
  1. A-band
  2. H-zone
  3. Z-line
  4. M-line

Answer: (B) H-zone

According to sliding filament theory, actin filaments slide over myosin, narrowing the I-band and causing the H-zone to shorten/disappear.

Q31. Which of the following is a non-steroidal oral contraceptive pill developed by CDRI, Lucknow?
  1. Mala-D
  2. Mala-N
  3. Saheli
  4. Progestasert

Answer: (C) Saheli

Saheli is a once-a-week non-steroidal oral contraceptive pill developed by CDRI, Lucknow.

Q32. In human circulatory system, oxygenated blood from lungs enters which heart chamber?
  1. Right Atrium
  2. Right Ventricle
  3. Left Atrium
  4. Left Ventricle

Answer: (C) Left Atrium

Pulmonary veins carry oxygenated blood from lungs directly into the Left Atrium of the heart.