Chemistry
- 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
- Which one of the following conditions will favour maximum formation of the product in the reaction,A_2(g) + B_2(g) ⇌ X_2(g) Δ_rH = -X kJ ? Answer: 1. Low temperature and high pressure Apply Le Chatelier's principle to A₂+B₂⇌ X₂ , which is exothermic and reduces the number of gas... 1
- The correction factor 'a' to the ideal gas equation corresponds to Answer: 4. forces of attraction between the gas molecules In the van der Waals equation (P+an²/V²)(V-nb)=nRT , the term a corrects the press... 1
- Hydrocarbon (A) reacts with bromine by substitution to form an alkyl bromide which by Wurtz reaction is converted to gaseous hydrocarbon containing less than four carbon atoms. (A) is Answer: 4. CH ₄ The alkyl bromide undergoes Wurtz coupling, mathrm2R-Br+2Na→ R-R+2NaBr . The product has twice the carbon count of R, and mu... 1
- The compound C_7H_8 undergoes the following reactions :C_7H_8 3\ Cl_2/Δ A Br_2/Fe B Zn/HCl CThe product 'C' is Answer: 1. m-bromotoluene Work through the sequence: C₇H₈ is toluene. 3 Cl₂/Δ : side-chain chlorination gives benzotrichloride, C₆H₅CCl₃ (A)... 1
- Identify the major products P, Q and R in the following sequence of reactions :benzene + CH_3CH_2CH_2Cl Anhydrous AlCl_3 P ; P [(ii) H_3O^+/Δ](i) O_2 Q + R Answer: 4. P = cumene (C ₆ H ₅ CH(CH ₃ ) ₂ ), Q = phenol (C ₆ H ₅ OH), R = CH ₃ - CO - CH ₃ Friedel-Crafts alkylation with n-propyl chloride... 1
- The compound A on treatment with Na gives B, and with PCl_5 gives C. B and C react together to give diethyl ether. A, B and C are in the order Answer: 4. C ₂ H ₅ OH, C ₂ H ₅ ONa, C ₂ H ₅ Cl A is ethanol. C₂H₅OH+Na→ C₂H₅ONa (B), and C₂H₅OH+PCl₅→ C₂H₅Cl (C). B and C then react by Will... 1
- Which oxide of nitrogen is not a common pollutant introduced into the atmosphere both due to natural and human activity ? Answer: 1. N ₂ O ₅ N₂O , NO and NO₂ are all released by natural processes (soil bacteria, lightning) and by human activity (fuel combustion,... 1
- For the redox reactionMnO_4^- + C_2O_4^2- + H^+ Mn^2+ + CO_2 + H_2Othe correct coefficients of the reactants for the balanced equation are(columns: MnO_4^-, C_2O_4^2-, H^+) Answer: 3. 2, 5, 16 Balance by the ion-electron method. Reduction: mathrmMnO₄^-+8H^++5e^-→ Mn²⁺+4H₂O . Oxidation: mathrmC₂O₄²⁻→2CO₂+2e^- . M... 1
- Consider the change in oxidation state of Bromine corresponding to different emf values as shown in the diagram below :BrO_4^- 1.82\ V BrO_3^- 1.5\ V HBrO 1.595\ V Br_2 1.0652\ V Br^-Then the species undergoing disproportionation is Answer: 4. HBrO A species disproportionates if the emf for its reduction (to the species on one side) is higher than the emf for its oxidati... 1
- In which case is the number of molecules of water maximum ? Answer: 1. 18 mL of water Compare the number of moles; more moles means more molecules. 18 mL water = 18 g (density 1 g/mL) = 1 mol. 0.00224... 1
- Which of the following carbocations is expected to be most stable ? Answer: 2. cyclohexadienyl cation with NO ₂ at top carbon, H and Y on the sp ³ carbon, positive charge adjacent (picture) In the intermediat... 1