Chemistry
- 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
- 4d, 5p, 5f and 6p orbitals are arranged in the order of decreasing energy. The correct option is : Answer: 1. 5f > 6p > 5p > 4d Orbital energy in a many-electron atom follows the (n+l) rule; if (n+l) is equal, the orbital with lower n has... 1
- The non-essential amino acid among the following is : Answer: 3. alanine Essential amino acids cannot be made by the body and must come from food: valine, leucine, lysine (and isoleucine, etc.).... 1
- Which of the following diatomic molecular species has only π bonds according to Molecular Orbital Theory ? Answer: 3. C ₂ Write the MO configuration for each molecule. C₂ (12 electrons): σ_1s²σ_1s^(*2)σ_2s²σ_2s^(*2)π_2p⁴ . The 2p electrons occupy... 1
- If the rate constant for a first order reaction is k, the time (t) required for the completion of 99% of the reaction is given by : Answer: 3. t = 4.606/k For a first order reaction t = 2.303/klog[A]₀/[A] . When 99% is complete, [A] = 0.01[A]₀ , so t = 2.303/klog 100 = 2.... 1
- Under isothermal condition, a gas at 300 K expands from 0.1 L to 0.25 L against a constant external pressure of 2 bar. The work done by the gas is :[Given that 1 L bar = 100 J] Answer: 4. 30 J Key idea: for expansion against a constant external pressure, the magnitude of work is p_extΔ V , and the question asks for... 1
- For the second period elements the correct increasing order of first ionisation enthalpy is : Answer: 2. Li < B < Be < C < O < N < F < Ne First ionisation enthalpy generally increases across a period, with two exceptions in period 2.... 1
- Enzymes that utilize ATP in phosphate transfer require an alkaline earth metal (M) as the cofactor. M is : Answer: 2. Mg ATP-utilising enzymes (phosphate transfer) need mathrmMg²⁺ as cofactor; Mg binds the phosphate groups of ATP. Ca is mainly inv... 1
- pH of a saturated solution of Ca(OH)_2 is 9. The solubility product (K_sp) of Ca(OH)_2 is : Answer: 1. 0.5×10⁻¹⁵ Use pH to get [OH^-] , then write K_sp . pH = 9 so pOH = 5 and [OH^-] = 10⁻⁵ M. mathrmCa(OH)₂ ⇌ Ca²⁺ + 2OH^- , so [math... 1
- The most suitable reagent for the following conversion, is :H_3C-C C-CH_3 → cis-2-butene Answer: 2. H ₂ , Pd/C, quinoline Partial reduction of an alkyne to a cis-alkene needs syn addition of H₂ on a poisoned catalyst, i.e. Lindla... 1
- The structure of intermediate A in the following reaction, is :[Reaction: cumene (isopropylbenzene) O_2 A [H_2O]H^+ phenol + acetone] Answer: 2. (2) cumene hydroperoxide: C6H5-C(CH3)2-O-O-H In the cumene process, cumene is oxidised by air at the benzylic tertiary C-H bond t... 1
- Among the following, the one that is not a green house gas is : Answer: 4. sulphur dioxide Greenhouse gases absorb infrared radiation re-emitted by the Earth. N₂O , CH₄ and O₃ (and CO₂ , CFCs) all do. SO₂... 1
- Which of the following is incorrect statement ? Answer: 1. PbF ₄ is covalent in nature Go through the statements. PbF₄ is ionic (Pb(IV) with the very electronegative F), so the statement '... 1
- Match the following :(a) Pure nitrogen (i) Chlorine(b) Haber process (ii) Sulphuric acid(c) Contact process (iii) Ammonia(d) Deacon's process (iv) Sodium azide or Barium azideWhich of the following is the correct option ? Answer: 4. (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i) (a) Pure nitrogen: obtained by heating sodium azide or barium azide, (iv). (b) Haber proce... 1
- Which is the correct thermal stability order for H_2E (E = O, S, Se, Te and Po) ? Answer: 3. H ₂ Po < H ₂ Te < H ₂ Se < H ₂ S < H ₂ O Thermal stability of hydrides of group 16 depends on the E-H bond strength, which falls... 1
- The correct structure of tribromooctaoxide is : Answer: 1. (structure 1, see figure) Tribromooctaoxide is the neutral molecule Br₃O₈ with a Br-Br-Br chain. The figure shows the structure w... 1
- For the cell reaction2Fe^3+(aq) + 2I^-(aq) → 2Fe^2+(aq) + I_2(aq)E^_cell = 0.24 V at 298 K. The standard Gibbs energy (Δ_rG^) of the cell reaction is :[Given that Faraday constant F = 96500 C mol^-1] Answer: 1. -46.32 kJ mol ⁻¹ Formula: Δ_rG^(ominus) = -nFE^(ominus)_cell . In the reaction 2mathrmFe³⁺ + 2I^- → 2mathrmFe²⁺ + I₂ , 2 electron... 1
- Which of the following reactions are disproportionation reaction ?(a) 2Cu^+ → Cu^2+ + Cu^0(b) 3MnO_4^2- + 4H^+ → 2MnO_4^- + MnO_2 + 2H_2O(c) 2KMnO_4 Δ K_2MnO_4 + MnO_2 + O_2(d) 2MnO_4^- + 3Mn^2+ + 2H_2O → 5MnO_2 + 4H^Select the correct option from th… Answer: 1. (a) and (b) only A disproportionation reaction is one in which the same species is both oxidised and reduced. (a) mathrmCu^+ → Cu... 1
- The biodegradable polymer is : Answer: 2. nylon 2-nylon 6 Nylon 2-nylon 6 is a copolymer of glycine and amino caproic acid joined by peptide (amide) linkages that enzymes... 1
- The number of sigma (σ) and pi (π) bonds in pent-2-en-4-yne is : Answer: 1. 10 σ bonds and 3 π bonds Count every bond in pent-2-en-4-yne, CH₃-CH=CH-Cequiv CH . A single bond is one σ ; a double bond is 1 σ... 1
- Which one is a wrong statement ? Answer: 2. The electronic configuration of N atom is1s ² 2s ² 2p _x¹ 2p _y¹ 2p _z¹ shown as orbital box diagram: 1s [up down], 2s [up down],... 1