onic configurations belong to main group elements? A. [Ne]3s¹, B. [Ar]3d³4s², C. [Kr]4d¹⁰5s²5p⁵, D. [Ar]3d¹⁰4s¹, E. [Rn]5f⁰6d²7s².","options":["B and E only","A and C only","D and E only","A, C and D only"],"answer":2,"why":"[Ne]3s¹ (Na, s-block) and [Kr]4d¹⁰5s²5p⁵ (I, p-block) are main-group; B and D are transition metals and E is inner-transition.","simPath":"Class-11/Chemistry/Chapter-3/prompt-31-spdf-block-configurations","simTitle":"s-p-d-f Block Configurations"},{"qNum":54,"topic":"Some Basic Concepts","question":"Dalton's atomic theory could not explain which of the following?","options":["Law of conservation of mass","Law of constant proportion","Law of multiple proportion","Law of gaseous volume"],"answer":4,"why":"Dalton's theory explains mass conservation and the proportion laws but not Gay-Lussac's law of combining gaseous volumes.","simPath":"Class-11/Chemistry/Chapter-1/prompt-29-laws-chemical-combination","simTitle":"Laws of Chemical Combination"},{"qNum":55,"topic":"Redox Reactions","question":"Consider KO₂, H₂O₂ and H₂SO₄. The oxidation states of the underlined elements (K, O, S) in them are, respectively:","options":["+1, −1, and +6","+2, −2, and +6","+1, −2, and +4","+4, −4, and +6"],"answer":1,"why":"K in KO₂ is +1, O in the peroxide H₂O₂ is −1, and S in H₂SO₄ is +6.","simPath":"Class-11/Chemistry/Chapter-7/problem-7.01-assign-oxidation-number-to-the-underlined-elements","simTitle":"Oxidation Numbers"},{"qNum":56,"topic":"Chemical Kinetics","question":"If the half-life (t₁/₂) for a first-order reaction is 1 minute, then the time required for 99.9% completion of the reaction is closest to:","options":["2 minutes","4 minutes","5 minutes","10 minutes"],"answer":4,"why":"99.9% completion leaves 1/1000, i.e. about 10 half-lives (2¹⁰ ≈ 1000), so ≈10 minutes.","simPath":"Class-12/Chemistry/Chapter-3/example-3.07-theory-half-life-of-a-reaction","simTitle":"First-Order Half-Life"},{"qNum":57,"topic":"Coordination Compounds","question":"The correct order of the wavelength of light absorbed by A. [Co(NH₃)₆]³⁺, B. [Co(CN)₆]³⁻, C. [Cu(H₂O)₄]²⁺, D. [Ti(H₂O)₆]³⁺ is:","options":["B < D < A < C","B < A < D < C","C < D < A < B","C < A < D < B"],"answer":2,"why":"Larger Δ₀ absorbs shorter λ; Δ order B > A > D > C, so wavelength order is B < A < D < C.","simPath":"Class-12/Chemistry/Chapter-5/problem-5.31-wavelength-order-ni-complexes","simTitle":"CFT Wavelength Order"},{"qNum":58,"topic":"Stereochemistry","question":"Which one of the following compounds can exist as cis-trans isomers?","options":["Pent-1-ene","2-Methylhex-2-ene","1,1-Dimethylcyclopropane","1,2-Dimethylcyclohexane"],"answer":4,"why":"1,2-Dimethylcyclohexane has two different groups on each of two ring carbons, giving cis and trans forms; the others lack the required geometric restriction.","simPath":"Class-12/Chemistry/Chapter-5/problem-5.09-geometrical-isomers-count","simTitle":"Geometric Isomerism"},{"qNum":59,"topic":"Ionic Equilibrium","question":"Phosphoric acid ionizes in three steps with constants Ka₁, Ka₂, Ka₃, and K is the overall ionization constant. Which statements are true? A. log K = log Ka₁ + log Ka₂ + log Ka₃. B. H₃PO₄ is a stronger acid than H₂PO₄⁻ and HPO₄²⁻. C. Ka₁ > Ka₂ > Ka₃. D. Ka₁ = (Ka₃ + Ka₂)/2.","options":["A and B only","A and C only","B, C and D only","A, B and C only"],"answer":4,"why":"Overall K = Ka₁·Ka₂·Ka₃ (A), successive Ka values decrease so H₃PO₄ is strongest (B, C); D is a false relation.","simPath":"Class-11/Chemistry/Chapter-6/problem-6.45-diprotic-acid-stepwise-ionization","simTitle":"Stepwise Ionization"},{"qNum":60,"topic":"Hydrocarbons","question":"Which one of the following reactions does NOT give benzene as the product?","options":["Sodium benzoate + soda lime, Δ","n-hexane with Mo₂O₃, 773 K, 10–20 atm","Ethyne (HC≡CH) through a red-hot iron tube at 873 K","Benzenediazonium chloride with H₂O, warm"],"answer":4,"why":"Benzenediazonium chloride hydrolyses t

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