NEET UG
- Plants having little or no secondary growth are Answer: 1. Grasses Secondary growth depends on a vascular cambium, which is weak or absent in monocots. Grasses are monocots with closed vas... 1
- Casparian strips occur in Answer: 4. Endodermis Casparian strips are waterproof bands of suberin on the radial and tangential walls of endodermal cells. They force wa... 1
- Secondary xylem and phloem in dicot stem are produced by Answer: 3. Vascular cambium Secondary growth in a dicot stem is by the lateral meristem called vascular cambium. Vascular cambium cuts secon... 1
- In India, the organisation responsible for assessing the safety of introducing genetically modified organisms for public use is Answer: 4. Genetic Engineering Appraisal Committee (GEAC) In India GEAC (Genetic Engineering Appraisal Committee) decides on the safety of G... 1
- Use of bioresources by multinational companies and organisations without authorisation from the concerned country and its people is called Answer: 3. Biopiracy Using biological resources or related knowledge without proper authorisation and payment is called biopiracy. Biodegrad... 1
- A ‘new’ variety of rice was patented by a foreign company, though such varieties have been present in India for a long time. This is related to Answer: 4. Basmati A foreign company patented Basmati rice (a US patent to RiceTec), though India has grown basmati for centuries. Co-667 is... 1
- The correct order of steps in Polymerase Chain Reaction (PCR) is Answer: 4. Denaturation, Annealing, Extension PCR is a cycle of three steps in a fixed order: denaturation, annealing, extension. Heat (abou... 1
- Which of the following is commonly used as a vector for introducing a DNA fragment in human lymphocytes ? Answer: 1. Retrovirus To put a gene into animal cells such as human lymphocytes, disarmed retroviruses are used as vectors. Retroviruses inf... 1
- Which of the following statements is *correct* ? Answer: 1. Ovules are not enclosed by ovary wall in gymnosperms. Gymnosperms are 'naked-seeded' plants, so their ovules lie exposed and are... 1
- Pneumatophores occur in Answer: 1. Halophytes Pneumatophores are breathing roots that grow upward out of waterlogged, salty soil. They are found in mangrove plants... 1
- Which one is a wrong statement ? Answer: 2. The electronic configuration of N atom is1s ² 2s ² 2p _x¹ 2p _y¹ 2p _z¹ shown as orbital box diagram: 1s [up down], 2s [up down],... 1
- Which of the following compounds can form a zwitterion ? Answer: 4. Glycine A zwitterion needs both an acidic group and a basic group in the same molecule, so the proton moves from the acid to the... 1
- Among CaH_2, BeH_2, BaH_2, the order of ionic character is Answer: 1. BeH ₂ < CaH ₂ < BaH ₂ Ionic character of a metal hydride increases with the electropositive (metallic) character of the metal, wh... 1
- Magnesium reacts with an element (X) to form an ionic compound. If the ground state electronic configuration of (X) is 1s^2 2s^2 2p^3, the simplest formula for this compound is Answer: 4. Mg ₃ X ₂ X has configuration 1s²2s²2p³ , so it is nitrogen and forms mathrmX³⁻ . Magnesium forms mathrmMg²⁺ . Balancing charges:... 1
- Iron exhibits bcc structure at room temperature. Above 900°C, it transforms to fcc structure. The ratio of density of iron at room temperature to that at 900°C (assuming molar mass and atomic radii of iron remains constant with temperature) is Answer: 2. 3√(3)/4√(2) Density =Z M/a³ N_A . Since M and atomic radius r are the same, compare Z/a³ . bcc: Z=2 , a=4r/sqrt3 . fcc: Z=4 , a=2... 1
- Consider the following species :CN^+, CN^-, NO and CNWhich one of these will have the highest bond order ? Answer: 3. CN ^- Count electrons and fill the molecular orbitals. CN^- : 14 electrons, bond order 3 (isoelectronic with N₂ , CO). CN: 13 ele... 1
- The correct difference between first- and second-order reactions is that Answer: 3. the half-life of a first-order reaction does not depend on [A] ₀ ; the half-life of a second-order reaction does depend on [A] ₀... 1
- When initial concentration of the reactant is doubled, the half-life period of a zero order reaction Answer: 3. is doubled For a zero-order reaction, t_(1/2)=[A]₀/2k , directly proportional to the initial concentration. If [A]₀ is doubled, t... 1
- The bond dissociation energies of X_2, Y_2 and XY are in the ratio of 1 : 0.5 : 1. ΔH for the formation of XY is -200 kJ mol^-1. The bond dissociation energy of X_2 will be Answer: 2. 800 kJ mol ⁻¹ Let the bond energies be X-X = a , Y-Y = 0.5a , X-Y = a . For 1/2X₂+1/2Y₂→XY : Δ H=1/2 a+1/2(0.5a)-a=-0.25a . -0.25... 1
- Which one of the following ions exhibits d-d transition and paramagnetism as well ? Answer: 4. MnO ₄²⁻ d-d transitions need partly filled d orbitals; paramagnetism needs unpaired electrons. mathrmCrO₄²⁻ : Cr(+6), d⁰ . MnO₄^-... 1
- Match the metal ions given in Column I with the spin magnetic moments of the ions given in Column II and assign the correct code :Column I: a. Co^3+; b. Cr^3+; c. Fe^3+; d. Ni^2+Column II: i. √(8) B.M.; ii. √(35) B.M.; iii. √(3) B.M.; iv. √(24) B.M.;… Answer: 1. a-iv, b-v, c-ii, d-i Use μ=√(n(n+2)) with n unpaired electrons. mathrmCo³⁺ ( d⁶ , high spin, n = 4): √(24) (iv). mathrmCr³⁺ ( d³... 1
- The type of isomerism shown by the complex [CoCl_2(en)_2] is Answer: 1. Geometrical isomerism [CoCl₂(en)₂] is octahedral of type [M(AA)₂X₂] . The two Cl can be adjacent (cis) or opposite (trans), so it... 1
- The geometry and magnetic behaviour of the complex [Ni(CO)_4] are Answer: 3. tetrahedral geometry and diamagnetic In [Ni(CO)₄] Ni is in the zero oxidation state with configuration 3d⁸ 4s² . CO is a strong-f... 1
- Iron carbonyl, Fe(CO)_5 is Answer: 3. mononuclear Fe(CO)₅ contains one metal atom, so it is mononuclear. Dinuclear and polynuclear carbonyls like mathrmMn₂(CO)₁₀ and m... 1