NEET UG
- On balancing the given redox reaction,a Cr_2O_7^2- + b SO_3^2-(aq) + c H^+(aq) → 2a Cr^3+(aq) + b SO_4^2-(aq) + c2H_2O()the coefficients a, b and c are found to be, respectively - Answer: 2. 1, 3, 8 Key idea: Balance by the ion-electron (or oxidation-number) method. Cr goes from +6 to +3: gain of 3 e ^- per Cr, 6 e ^-... 1
- Upon exposure to UV radiation, DNA stained with ethidium bromide will show Answer: 1. Bright orange colour Key idea: DNA stained with ethidium bromide and exposed to UV light fluoresces as bright orange bands. This... 1
- Select the correct statements from the following :A. Atoms of all elements are composed of two fundamental particles.B. The mass of the electron is 9.10939 × 10^-31 kg.C. All the isotopes of a given element show same chemical properties.D. Protons an… Answer: 1. B, C and E only Key idea: Check each statement. A. False: atoms are made of three fundamental particles (electron, proton, neutro... 1
- The relation between n_m, (n_m = the number of permissible values of magnetic quantum number (m)) for a given value of azimuthal quantum number (l), is Answer: 2. l = n_m - 1/2 Key idea: For a given l , m takes values from -l to +l including 0. Number of values: n_m = 2l + 1 . Rearranging, l... 1
- What fraction of one edge centred octahedral void lies in one unit cell of fcc? Answer: 4. 1/4 Key idea: An octahedral void at an edge centre is shared by the 4 unit cells meeting at that edge. An fcc cell has one octahe... 1
- Amongst the following, the total number of species NOT having eight electrons around central atom in its outer most shell, isNH_3, AlCl_3, BeCl_2, CCl_4, PCl_5 : Answer: 2. 3 Key idea: Count the electrons in the valence shell of the central atom. NH₃ : 8 (3 bond pairs + 1 lone pair). AlCl₃ : 6 (incomp... 1
- Intermolecular forces are forces of attraction and repulsion between interacting particles that will include :A. dipole - dipole forces.B. dipole - induced dipole forces.C. hydrogen bonding.D. covalent bonding.E. dispersion forces.Choose the most app… Answer: 4. A, B, C, E are correct. Key idea: Intermolecular forces act between molecules; covalent bonds are intramolecular. Dipole-dipole (... 1
- The number of σ bonds, π bonds and lone pair of electrons in pyridine, respectively are : Answer: 4. 11, 3, 1 Key idea: Count bonds in pyridine, C₅H₅N (a six-membered ring with 3 C=C/C=N double bonds). σ bonds: 6 ring bonds + 5 C-... 1
- Which amongst the following options is the correct relation between change in enthalpy and change in internal energy? Answer: 3. Δ H = Δ U + Δ n_g RT Key idea: H = U + PV , so at constant T and P, Δ H = Δ U + PΔ V = Δ U + Δ n_g RT . Here Δ n_g is the change... 1
- Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R :Assertion A : Metallic sodium dissolves in liquid ammonia giving a deep blue solution, which is paramagnetic.Reasons R : The deep blue solution is… Answer: 4. A is true but R is false. Key idea: Sodium in liquid ammonia gives ammoniated electrons. Na + (x+y)NH₃ → [Na(NH₃)_x]^+ + [e(NH₃)_... 1
- Homoleptic complex from the following complexes is : Answer: 2. Potassium trioxalatoaluminate (III) Key idea: A homoleptic complex has only one kind of ligand bonded to the metal. Potassium tri... 1
- Which of the following statements are INCORRECT?A. All the transition metals except scandium form MO oxides which are ionic.B. The highest oxidation number corresponding to the group number in transition metal oxides is attained in Sc_2O_3 to Mn_2O_7… Answer: 4. C and D only Key idea: Recall the d-block oxide trends. A. Correct: MO oxides (except Sc) are ionic. B. Correct: the group oxidat... 1
- Amongst the given options which of the following molecules / ion acts as a Lewis acid? Answer: 4. BF ₃ Key idea: A Lewis acid accepts an electron pair. BF₃ has an incomplete octet on boron (6 electrons) and an empty p orbital,... 1
- Which amongst the following molecules on polymerization produces neoprene? Answer: 3. H₂C=C(Cl)-CH=CH₂ Key idea: Neoprene is a polymer of chloroprene, 2-chlorobuta-1,3-diene. Chloroprene is CH₂=C(Cl)-CH=CH₂ , which... 1
- Identify the final product [D] obtained in the following sequence of reactions.CH_3CHO [ii)\ H_3O^+]i)\ LiAlH_4 [A] [Δ]H_2SO_4 [B] HBr [C], then [C] + bromobenzene Na/dry\ ether [D] Answer: 2. ethylbenzene (structure) Key idea: Follow the sequence, ending with a Wurtz-Fittig reaction. CH₃CHO with LiAlH₄ gives ethanol [A]... 1
- Which of the following reactions will NOT give primary amine as the product? Answer: 4. mathrmCH₃NC xrightarrow[(ii)\ H₃O^(oplus)](i)\ LiAlH₄ Product Key idea: Find which reaction does not give R-NH₂ . 1: LiAlH₄ reduc... 1
- Consider the following reaction and identify the product (P).CH_3-CH(CH_3)-CH(OH)-CH_3 (3 - Methylbutan-2-ol) HBr Product (P) Answer: 2. CH₃-C(Br)(CH₃)-CH₂-CH₃ Key idea: A secondary alcohol with HBr reacts through a carbocation ( S_N1 ), which can rearrange to a mor... 1
- Which amongst the following will be most readily dehydrated under acidic conditions ? Answer: 3. skeletal structure (3) bearing two OH, H ₃ C and H (see figure) Key idea: Acid-catalysed dehydration of an alcohol goes through a... 1
- Identify product (A) in the following reaction :3-(3-acetylphenyl)-substituted cyclohexyl methyl ketone: a cyclohexane ring bearing an acetyl group, joined to a benzene ring bearing an acetyl group (meta), [conc. HCl]Zn-Hg (A) + 2H_2O Answer: 2. both acetyl groups reduced to ethyl groups (structure) Key idea: Zn-Hg/conc. HCl is the Clemmensen reduction, which converts >C=O... 1
- Consider the following reaction :C_6H_5-CH_2-O-C_6H_5 [Δ]HI A + B (benzyl phenyl ether)Identify products A and B. Answer: 4. A = C ₆ H ₅ -CH ₂ I and B = C ₆ H ₅ -OH Key idea: HI cleaves an aryl alkyl ether at the alkyl-oxygen bond, because the aryl C-O b... 1
- Identify the major product obtained in the following reaction :2-acetylbenzaldehyde (benzene ring with ortho -COCH_3 and -CHO) + 2[Ag(NH_3)_2]^+ + 3 ^-OH Δ major product Answer: 4. ring with -COCH ₃ and -COO ^- (structure) Key idea: Tollens' reagent [Ag(NH₃)₂]^+ in base is a mild oxidant: it oxidises aldehyde... 1
- Given below are two statements :Statement I : The nutrient deficient water bodies lead to eutrophication.Statement II : Eutrophication leads to decrease in the level of oxygen in the water bodies.In the light of the above statements, choose the corre… Answer: 1. Statement I is incorrect but Statement II is true. Key idea: Eutrophication is caused by nutrient enrichment. Statement I is fals... 1
- Match List - I with List - II :List - I (Oxoacids of Sulphur): A. Peroxodisulphuric acid B. Sulphuric acid C. Pyrosulphuric acid D. Sulphurous acidList - II (Bonds): I. Two S-OH, Four S=O, One S-O-S II. Two S-OH, One S=O III. Two S-OH, Four S=O, One… Answer: 3. A-III, B-IV, C-I, D-II Key idea: Draw the structure of each oxoacid. A. H₂S₂O₈ , peroxodisulphuric: two S-OH, four S=O and one S-... 1
- Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R :Assertion A : In equation Δ_r G = -nFE_cell, value of Δ_r G depends on n.Reasons R : E_cell is an intensive property and Δ_r G is an extensive prop… Answer: 2. Both A and R are true and R is the correct explanation of A. Key idea: Δ_rG = -nFE_cell links an extensive quantity to an intensi... 1