#neet
- The equation of Verhulst-Pearl logistic growth isdN/dt = rN≤ft[K-N/K].From this equation, K indicates: Answer: 4. Carrying capacity Key idea: in the Verhulst-Pearl logistic equation, K is the carrying capacity. In dN/dt=rN[K-N/K] , N is popula... 1
- How many molecules of ATP and NADPH are required for every molecule of CO_2 fixed in the Calvin cycle? Answer: 1. 3 molecules of ATP and 2 molecules of NADPH Key idea: fixing one CO₂ in the Calvin cycle costs 3 ATP and 2 NADPH. One CO₂ joins R... 1
- Match List I with List IIList I: A. Clostridium butylicum; B. Saccharomyces cerevisiae; C. Trichoderma polysporum; D. Streptococcus sp.List II: I. Ethanol; II. Streptokinase; III. Butyric acid; IV. Cyclosporin-AChoose the correct answer from the opti… Answer: 4. A-III, B-I, C-IV, D-II Key idea: match each microbe with the product it yields. Clostridium butylicum makes butyric acid (A-III).... 1
- These are regarded as major causes of biodiversity loss:A. Over exploitationB. Co-extinctionC. MutationD. Habitat loss and fragmentationE. MigrationChoose the correct option: Answer: 1. A, B and D only Key idea: the "evil quartet" of biodiversity loss is habitat loss and fragmentation, over-exploitation, alien spe... 1
- Given below are two statements:Statement I : Chromosomes become gradually visible under light microscope during leptotene stage.Statement II : The begining of diplotene stage is recognized by dissolution of synaptonemal complex.In the light of the ab… Answer: 2. Both Statement I and Statement II are true Key idea: recall what happens in each substage of prophase I. Statement I: In leptoten... 1
- Auxin is used by gardeners to prepare weed-free lawns. But no damage is caused to grass as auxin Answer: 4. does not affect mature monocotyledonous plants. Key idea: synthetic auxins like 2,4-D kill dicot weeds but not monocot crops or g... 1
- The highest number of helium atoms is in Answer: 2. 4 mol of helium Key idea: convert each to number of atoms (He is monoatomic). 2.271098 L at STP (22.7 L/mol): 0.1 mol. 4 mol: 4 m... 1
- The E^° value for the Mn^3+/Mn^2+ couple is more positive than that of Cr^3+/Cr^2+ or Fe^3+/Fe^2+ due to change of Answer: 4. d⁴ to d⁵ configuration Key idea: a high E^° for M³⁺/M²⁺ means M³⁺ is easily reduced to a very stable M²⁺ . mathrmMn³⁺ is d⁴ ; on... 1
- Given below are two statements :Statement I : Both [Co(NH_3)_6]^3+ and [CoF_6]^3- complexes are octahedral but differ in their magnetic behaviour.Statement II : [Co(NH_3)_6]^3+ is diamagnetic whereas [CoF_6]^3- is paramagnetic.In the light of the abo… Answer: 2. Both Statement I and Statement II are true. Key idea: the ligand field strength decides pairing in mathrmCo³⁺ ( d⁶ ). NH₃ is a st... 1
- Fehling's solution 'A' is Answer: 2. aqueous copper sulphate Key idea: Fehling's solution is prepared as two separate solutions. Fehling's A: aqueous copper sulphate.... 1
- In which of the following processes entropy increases?A. A liquid evaporates to vapour.B. Temperature of a crystalline solid lowered from 130 K to 0 K.C. 2NaHCO_3(s) → Na_2CO_3(s) + CO_2(g) + H_2O_(g)D. Cl_2(g) → 2Cl_(g)Choose the correct answer from… Answer: 4. A, C and D Key idea: entropy rises with disorder, i.e. when more gas or more particles are formed. A: liquid to vapour, disorder... 1
- The energy of an electron in the ground state (n = 1) for He^+ ion is -x J, then that for an electron in n = 2 state for Be^3+ ion in J is : Answer: 2. -x Key idea: for hydrogen-like ions E_n=-E₁(H) Z²/n² . For He^+ (Z=2), n=1: -x=-4E₀ , so E₀=x/4 . For mathrmBe³⁺ (Z=4), n=2: E=-E... 1
- Match List I with List II.List I (Reactions): A. [structure: bicyclohexylidene → 2 cyclohexanone] B. [structure: benzene → benzophenone] C. [structure: cyclohexanol → cyclohexanone] D. [structure: ethylbenzene → potassium benzoate]List II (Reagents/C… Answer: 4. A-IV, B-I, C-II, D-III Key idea: identify the reagent for each conversion. A: alkene to two ketones is ozonolysis, O₃ , then Zn-H... 1
- Activation energy of any chemical reaction can be calculated if one knows the value of Answer: 1. rate constant at two different temperatures. Key idea: from the Arrhenius equation, logk₂/k₁=E_a/2.303R(1/T₁-1/T₂) . Knowing k at... 1
- The most stable carbocation among the following is: Answer: 1. [structure: methylcyclohexyl carbocation, see figure] Key idea: carbocation stability: tertiary > secondary > primary, and more h... 1
- Given below are two statements:Statement I : The boiling point of three isomeric pentanes follows the ordern-pentane > isopentane > neopentaneStatement II : When branching increases, the molecule attains a shape of sphere. This results in smaller sur… Answer: 2. Both Statement I and Statement II are correct. Key idea: among isomers, more branching means a more spherical shape and a lower b... 1
- Which one of the following alcohols reacts instantaneously with Lucas reagent? Answer: 1. CH₃-C(CH₃)(CH₃)-OH (i.e. (CH₃)₃C-OH , drawn with CH₃ above and below the carbon) Key idea: Lucas reagent ( ZnCl₂ /conc. HCl) work... 1
- The Henry's law constant (K_H) values of three gases (A, B, C) in water are 145, 2×10^-5 and 35 kbar, respectively. The solubility of these gases in water follow the order: Answer: 3. B > C > A Key idea: by Henry's law p=K_Hx , so a larger K_H means lower solubility. K_H : B ( 2×10⁻⁵ ) < C (35) < A (145) kbar. S... 1
- Which plot of ln k vs 1/T is consistent with Arrhenius equation? Answer: 1. [graph option 1, see figure] Key idea: ln k=ln A-E_a/R·1/T , a straight line with negative slope -E_a/R and positive intercept ln... 1
- On heating, some solid substances change from solid to vapour state without passing through liquid state. The technique used for the purification of such solid substances based on the above principle is known as Answer: 3. Sublimation Key idea: sublimation is the conversion of solid directly into vapour. Solids like camphor, naphthalene and iodine ar... 1
- Intramolecular hydrogen bonding is present in Answer: 2. [structure: 2-nitrophenol (NO2 and OH on adjacent carbons), see figure] Key idea: intramolecular H-bonding needs the H-donor (-OH... 1
- 1 gram of sodium hydroxide was treated with 25 mL of 0.75 M HCl solution, the mass of sodium hydroxide left unreacted is equal to Answer: 3. 250 mg Key idea: find the limiting reagent for NaOH+HCl→ NaCl+H₂O . NaOH: 1/40=0.025 mol = 25 mmol. HCl: 25×0.75=18.75 mmol. Left... 1
- Which reaction is NOT a redox reaction? Answer: 1. BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl Key idea: a redox reaction has a change in oxidation numbers. BaCl₂+Na₂SO₄→ BaSO₄+2NaCl is a doubl... 1
- 'Spin only' magnetic moment is same for which of the following ions?A. Ti^3+ B. Cr^2+ C. Mn^2+ D. Fe^2+ E. Sc^3+Choose the most appropriate answer from the options given below: Answer: 2. B and D only Key idea: μ=√(n(n+2)) BM, so equal unpaired electrons give equal moment. mathrmTi³⁺ ( d¹ ): 1 mathrmCr²⁺ ( d⁴ ): 4 m... 1