NEET UG
- For the chemical reactionN_2(g) + 3H_2(g) ⇌ 2NH_3(g)the correct option is : Answer: 3. -d[N₂]/dt = 1/2d[NH₃]/dt Rate of reaction: divide the rate of change of each species by its stoichiometric coefficient (negative... 1
- In which case change in entropy is negative ? Answer: 4. 2H(g) → H ₂ (g) Entropy measures disorder. Evaporation, sublimation and isothermal expansion all increase randomness ( Δ S>0 ). I... 1
- Which of the following is an amphoteric hydroxide ? Answer: 4. Be(OH) ₂ Going down group 2, hydroxides become more basic. Sr(OH)₂ , Ca(OH)₂ and Mg(OH)₂ are basic. Be(OH)₂ dissolves in both aci... 1
- The method used to remove temporary hardness of water is : Answer: 2. Clark's method Key idea: temporary hardness is due to bicarbonates of Ca and Mg, and the method meant specifically for it is Clar... 1
- What is the correct electronic configuration of the central atom in K_4[Fe(CN)_6] based on crystal field theory ? Answer: 2. t_2g⁶e_g⁰ In K₄[Fe(CN)₆] iron is Fe(II), a d⁶ ion. CN^- is a strong field ligand, so the pairing energy is lower than Δ_o and all... 1
- The manganate and permanganate ions are tetrahedral, due to : Answer: 1. The π -bonding involves overlap of p-orbitals of oxygen with d-orbitals of manganese In MnO₄^- and mathrmMnO₄²⁻ , Mn uses sp³ hyb... 1
- Which one is malachite from the following ? Answer: 4. CuCO ₃ .Cu(OH) ₂ Malachite is the green basic copper carbonate CuCO₃· Cu(OH)₂ . CuFeS₂ is copper pyrites and Fe₃O₄ is magnetite.... 1
- Which will make basic buffer ? Answer: 3. 100 mL of 0.1 M HCl + 200 mL of 0.1 M NH ₄ OH A basic buffer is a weak base plus its salt (conjugate acid). (1) 5 mmol NaOH + 2.5... 1
- Conjugate base for Brönsted acids H_2O and HF are : Answer: 3. OH ^- and F ^- , respectively A conjugate base is formed when the acid loses H^+ . H₂O → OH^- + H^+ and HF → F^- + H^+ . So the c... 1
- An alkene "A" on reaction with O_3 and Zn-H_2O gives propanone and ethanal in equimolar ratio. Addition of HCl to alkene "A" gives "B" as the major product. The structure of product "B" is : Answer: 3. H ₃ C-CH ₂ -C(CH ₃ )(Cl)-CH ₃ (see figure) Work back from the ozonolysis products. Propanone (CH₃)₂C=O and ethanal CH₃CHO join at... 1
- Among the following, the reaction that proceeds through an electrophilic substitution, is : Answer: 2. (structure 2, see figure): benzene + Cl ₂ xrightarrowAlCl₃ chlorobenzene + HCl (1) Sandmeyer reaction: via aryl radical / diazoni... 1
- The correct order of the basic strength of methyl substituted amines in aqueous solution is : Answer: 1. (CH₃)₂NH > CH₃NH₂ > (CH₃)₃N In aqueous solution basicity depends on both the inductive effect (more alkyl groups push electrons)... 1
- The major product of the following reaction is :phthalic acid (benzene-1,2-dicarboxylic acid) + NH_3 strong\ heating Answer: 2. phthalimide (see figure) Phthalic acid reacts with ammonia to give the ammonium salt; strong heating removes water in two steps (... 1
- The compound that is most difficult to protonate is : Answer: 4. Ph-O-H Protonation occurs on the oxygen lone pair; the more available the lone pair, the easier it is to protonate. H₂O , CH₃OH ,... 1
- Which of the following species is not stable ? Answer: 4. [SiCl₆]²⁻ Key idea: silicon (period 3) can expand its octahedral coordination, but only with small ligands. mathrm[SiF₆]²⁻ is kno... 1
- Identify the incorrect statement related to PCl_5 from the following : Answer: 4. PCl ₅ molecule is non-reactive PCl₅ is trigonal bipyramidal. Three equatorial P-Cl bonds are at 120 to each other: correct. Two a... 1
- Match the Xenon compounds in Column - I with its structure in Column - II and assign the correct code :Column - I: (a) XeF_4 (b) XeF_6 (c) XeOF_4 (d) XeO_3Column - II: (i) pyramidal (ii) square planar (iii) distorted octahedral (iv) square pyramidalC… Answer: 2. (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i) (a) XeF₄ : square planar, (ii) (b) XeF₆ : distorted octahedral, (iii) (c) XeOF₄ : square p... 1
- Which mixture of the solutions will lead to the formation of negatively charged colloidal [AgI]I^- sol. ? Answer: 1. 50 mL of 1 M AgNO ₃ + 50 mL of 1.5 M KI or 2. 50 mL of 1 M AgNO ₃ + 50 mL of 2 M KI In the sol [AgI]I^- , AgI adsorbs the common... 1
- For a cell involving one electron E^_cell = 0.59 V at 298 K, the equilibrium constant for the cell reaction is :[Given that 2.303 RT/F = 0.059 V at T = 298 K] Answer: 3. 1.0×10¹⁰ At 298 K, E^(ominus)_cell = 0.059/nlog K . log K = dfracnE^(ominus)0.059 = 1×0.59/0.059 = 10 , so K = 1.0×10¹⁰ . Option... 1
- The mixture that forms maximum boiling azeotrope is : Answer: 1. Water + Nitric acid Maximum boiling azeotropes come from solutions with negative deviation from Raoult's law. Nitric acid and wat... 1
- For an ideal solution, the correct option is : Answer: 3. Δ_mixH = 0 at constant T and P For an ideal solution the A-B interactions equal the A-A and B-B interactions. Therefore Δ_mixH =... 1
- The number of moles of hydrogen molecules required to produce 20 moles of ammonia through Haber's process is : Answer: 3. 30 N₂ + 3H₂ → 2NH₃ : 3 mol H₂ give 2 mol NH₃ . Moles of H₂ = 20×3/2 = 30 . Option (3). 1
- A gas at 350 K and 15 bar has molar volume 20 percent smaller than that for an ideal gas under the same conditions. The correct option about the gas and its compressibility factor (Z) is : Answer: 3. Z < 1 and attractive forces are dominant Compressibility factor Z = V_real/V_ideal . The molar volume is 20% smaller, so V_real =... 1
- Colostrum, the yellowish fluid, secreted by mother during the initial days of lactation is very essential to impart immunity to the newborn infants because it contains : Answer: 4. Immunoglobulin A Colostrum is rich in antibodies, mainly IgA, which give the newborn passive natural immunity. NK cells, monocyte... 1