#neet
- Which of the following is the least likely to be involved in stabilizing the three-dimensional folding of most proteins? Answer: 3. Ester bonds Protein 3D structure is stabilised by hydrogen bonds, hydrophobic interactions, ionic (electrostatic) interactions an... 1
- Which of the following describes the given graph correctly? Answer: 1. Exothermic reaction with energy A in presence of enzyme and B in absence of enzyme The graph shows energy released, and the arrow... 1
- When cell has stalled DNA replication fork, which checkpoint should be predominantly activated? Answer: 1. G ₂ /M A stalled replication fork means DNA is not fully replicated. The cell must delay entry into mitosis until replication and... 1
- Which one of the following is incorrect for ideal solution? Answer: 3. Δ G_mix=0 Key idea: an ideal solution has no net interaction change on mixing, and mixing is spontaneous. Δ H_mix=0 and Δ U_mix=0... 1
- The solubility of AgCl (s) with solubility product 1.6×10^-10 in 0.1 M NaCl solution would be Answer: 1. 1.6×10⁻⁹ M Key idea: the common ion Cl^- from NaCl suppresses the solubility of AgCl. Let solubility be s . [Ag^+]=s , [Cl^-]≈ 0.... 1
- Suppose the elements X and Y combine to form two compounds XY_2 and X_3Y_2. When 0.1 mole of XY_2 weighs 10 g and 0.05 mole of X_3Y_2 weighs 9 g, the atomic weights of X and Y are Answer: 4. 40, 30 Key idea: molar mass = mass / moles, then form two equations in the atomic masses X and Y. XY₂ : M=10/0.1=100⇒ X+2Y=100 X₃... 1
- The number of electrons delivered at the cathode during electrolysis by a current of 1 ampere in 60 seconds is (charge on electron = 1.60×10^-19 C) Answer: 2. 3.75×10²⁰ Key idea: charge Q=It , and number of electrons =Q/e . Q=1×60=60\ C n=frac601.60×10⁻¹⁹=3.75×10²⁰ Option 4 ( 6×10²³ ) is... 1
- Boric acid is an acid because its molecule Answer: 2. accepts OH^- from water releasing proton Key idea: boric acid is a Lewis acid, not a proton donor. Boron in B(OH)₃ has an empty p... 1
- AlF_3 is soluble in HF only in presence of KF. It is due to the formation of Answer: 1. K₃[AlF₆] Key idea: AlF₃ is covalent and insoluble; extra F^- from KF forms a soluble complex. AlF₃+3KF→ K₃[AlF₆] The stable hexaf... 1
- Zinc can be coated on iron to produce galvanized iron but the reverse is not possible. It is because Answer: 3. zinc has higher negative electrode potential than iron Key idea: a more electropositive metal can protect a less electropositive... 1
- The hybridizations of atomic orbitals of nitrogen in NO_2^+, NO_3^- and NH_4^+ respectively are Answer: 2. sp , sp² and sp³ Key idea: hybridisation = (bond pairs + lone pairs) on N. NO₂^+ : O=N=O, 2 bond pairs, no lone pair, so sp . NO₃... 1
- Which of the following fluoro-compounds is most likely to behave as a Lewis base? Answer: 1. PF₃ Key idea: a Lewis base needs a lone pair to donate. PF₃ : P has a lone pair, so it can act as a donor. CF₄ : no lone pair and... 1
- Which of the following pairs of ions is isoelectronic and isostructural? Answer: Dropped in the official answer key: full marks to every candidate Key idea: compare total electrons and shape. CO₃²⁻ and NO₃^- : 32... 1
- In context with beryllium, which one of the following statements is incorrect? Answer: 2. Its salts rarely hydrolyze. Key idea: Be is small and highly polarising, so its salts hydrolyse readily. Be forms Be₂C (carbide):... 1
- Hot concentrated sulphuric acid is a moderately strong oxidizing agent. Which of the following reactions does not show oxidizing behaviour? Answer: 3. CaF₂ + H₂SO₄ → CaSO₄ + 2HF Key idea: oxidising behaviour means H₂SO₄ is reduced (S goes from +6 to +4 as SO₂ ). Options 1, 2, 4:... 1
- Which of the following pairs of d-orbitals will have electron density along the axes? Answer: 2. d_z², d_(x²-y²) Key idea: d_z² and d_(x²-y²) have lobes along the axes; d_xy, d_yz, d_xz have lobes between the axes. So the pair... 1
- The correct geometry and hybridization for XeF_4 are Answer: 3. square planar, sp³d² Key idea: Xe in XeF₄ has 4 bond pairs and 2 lone pairs. Steric number 6 gives sp³d² hybridisation and an oct... 1
- Among the following, which one is a wrong statement? Answer: 2. SeF₄ and CH₄ have same shape. Key idea: compare VSEPR shapes. SO₂ has pπ - dπ bonding: correct. SeF₄ is see-saw (4 bond pairs + 1... 1
- Genetic drift operates in Answer: 4. small isolated population Genetic drift is a random change in allele frequency due to chance. Its effect is strong in small isola... 1
- The highest DDT concentration in aquatic food chain shall occur in Answer: 1. seagull DDT is not broken down and builds up at each higher trophic level (biomagnification). The seagull is the top consumer her... 1
- Which of the following depicts the correct pathway of transport of sperms? Answer: 4. Rete testis → Efferent ductules → Epididymis → Vas deferens The sperm path is: seminiferous tubules, then rete testis, then effer... 1
- Match Column—I with Column—II and select the correct option using the codes given below :Column—I: a. Mons pubis; b. Antrum; c. Trophectoderm; d. NebenkernColumn—II: (i) Embryo formation; (ii) Sperm; (iii) Female external genitalia; (iv) Graafian fol… Answer: 1. (iii) (iv) (i) (ii) Mons pubis: fatty cushion over the pubic bone, part of the female external genitalia (iii). Antrum: fluid-fil... 1
- Several hormones like hCG, hPL, estrogen, progesterone are produced by Answer: 1. placenta The placenta is a temporary endocrine tissue during pregnancy. It makes hCG, hPL (human placental lactogen), estrogens a... 1
- If a colour-blind man marries a woman who is homozygous for normal colour vision, the probability of their son being colour-blind is Answer: 4. 0 Colour blindness is X-linked recessive. Let the normal allele be X and the defective allele X^c. Father: X^cY. Mother (homozygo... 1