#neet
- For a given reaction, Δ H = 35.5\ kJ\ mol^-1 and Δ S = 83.6\ JK^-1mol^-1. The reaction is spontaneous at : (Assume that Δ H and Δ S do not vary with temperature) Answer: 1. T > 425 K Key idea: a reaction is spontaneous when Δ G = Δ H - TΔ S < 0 . For Δ G<0 : T > Δ H/Δ S . T > dfrac35.5×10³\ mathrmJ mo... 1
- Identify A and predict the type of reaction. [Reactant: 3-bromoanisole (benzene ring with OCH3 and Br meta to each other) with NaNH2 gives A] Answer: 4. [structure: 3-aminoanisole (OCH3 and NH2 meta)] and substitution reaction Key idea: aryl halide with NaNH₂ reacts through a benzy... 1
- Which of the following is dependent on temperature ? Answer: 1. Molarity Key idea: a concentration term that uses volume changes with temperature, because volume changes. Molarity = moles of so... 1
- With respect to the conformers of ethane, which of the following statements is true ? Answer: 3. Both bond angles and bond length remains same Key idea: conformers differ only by rotation about the C-C single bond. Staggered a... 1
- Name the gas that can readily decolourise acidified KMnO_4 solution : Answer: 1. SO₂ Key idea: KMnO₄ is decolourised by a reducing gas. SO₂ is a reducing agent: 5SO₂ + 2MnO₄^- + 2H₂O → 5SO₄²⁻ + 2Mn²⁺ + 4H^+ . P... 1
- It is because of inability of ns^2 electrons of the valence shell to participate in bonding that : Answer: 4. Sn²⁺ is reducing while Pb⁴⁺ is oxidising Key idea: the inert pair effect makes the +2 state more stable than +4 in heavy group 14... 1
- Mechanism of a hypothetical reaction X_2 + Y_2 → 2XY is given below :(i) X_2 → X + X (fast)(ii) X + Y_2 ⇌ XY + Y (slow)(iii) X + Y → XY (fast)The overall order of the reaction will be : Answer: 3. 1.5 Key idea: the rate law comes from the slow step; intermediates must be replaced using the fast equilibrium. Rate = k[X][Y₂] (... 1
- The equilibrium constants of the following are :N_2 + 3H_2 ⇌ 2NH_3 K_1N_2 + O_2 ⇌ 2NO K_2H_2 + 1/2O_2 → H_2O K_3The equilibrium constant (K) of the reaction : 2NH_3 + 5/2O_2 K⇌ 2NO + 3H_2O, will be : Answer: 1. K₂K₃³/K₁ Key idea: combine reactions; reversing gives 1/K , multiplying by n gives Kⁿ , adding gives the product of K values. Tar... 1
- Which one is the wrong statement ? Answer: 3. The energy of 2s orbital is less than the energy of 2p orbital in case of Hydrogen like atoms. Key idea: in a hydrogen-like atom,... 1
- Which one of the following statements is not correct ? Answer: 1. The value of equilibrium constant is changed in the presence of a catalyst in the reaction at equilibrium. Key idea: a catalyst c... 1
- HgCl_2 and I_2 both when dissolved in water containing I^- ions the pair of species formed is : Answer: 2. HgI₄²⁻, I₃^- Key idea: HgI₂ dissolves in excess I^- and I₂ dissolves in I^- by complex formation. HgCl₂ + 2I^-→ HgI₂ (red precipi... 1
- The correct increasing order of basic strength for the following compounds is : [(I) aniline, (II) 4-nitroaniline, (III) 4-methylaniline] Answer: 3. II < I < III Key idea: basic strength depends on how available the lone pair on N is. -CH₃ is electron-donating (+I, hyperconjuga... 1
- An example of a sigma bonded organometallic compound is : Answer: 1. Grignard's reagent Key idea: in a sigma-bonded organometallic compound, a metal-carbon sigma bond is present. Grignard's reagent,... 1
- A 20 litre container at 400 K contains CO_2(g) at pressure 0.4 atm and an excess of SrO (neglect the volume of solid SrO). The volume of the container is now decreased by moving the movable piston fitted in the container. The maximum volume of the co… Answer: 4. 5 litre Key idea: for SrCO₃(s)⇌ SrO(s)+CO₂(g) , K_p = p_(CO_2) at equilibrium, so the maximum pressure of CO₂ is 1.6 atm. Initial... 1
- Mixture of chloroxylenol and terpineol acts as : Answer: 1. antiseptic Key idea: a chloroxylenol and terpineol mixture is the well-known disinfectant Dettol. It is used on skin and wounds t... 1
- Pick out the correct statement with respect to [Mn(CN)_6]^3- : Answer: 2. It is d²sp³ hybridised and octahedral Key idea: cyanide is a strong-field ligand, which pairs the d electrons. In [Mn(CN)₆]³⁻ , M... 1
- If the E^°_cell for a given reaction has a negative value, which of the following gives the correct relationships for the values of Δ G^° and K_eq? Answer: 4. Δ G^° > 0 ; K_eq < 1 Key idea: Δ G^°=-nFE^°_cell=-RTln K . If E^°_cell<0 , then Δ G^°>0 , so ln K<0 and K_eq<1 . The reaction is... 1
- How many electrons can fit in the orbital for which n = 3 and l = 1? Answer: 4. 2 Key idea: one orbital holds at most 2 electrons (Pauli principle). n=3,l=1 is the 3p subshell, which has 3 orbitals (6 electron... 1
- The correct increasing order of trans-effect of the following species is Answer: 1. CN^- > C₆H₅^- > Br^- > NH₃ Key idea: trans-effect series: strong pi-acceptors and strong sigma-donors are highest, while NH₃ is l... 1
- Which one of the following statements related to lanthanons is incorrect? Answer: 2. All the lanthanons are much more reactive than aluminium. Key idea: check each statement against NCERT facts on lanthanoids. Stat... 1
- Jahn-Teller effect is not observed in high spin complexes of Answer: 1. d⁸ Key idea: Jahn-Teller distortion occurs when the e_g or t_2g set is unevenly filled (degenerate ground state). High spin d⁸ :... 1
- Which of the following can be used as the halide component for Friedel-Crafts reaction? Answer: 3. Isopropyl chloride Key idea: Friedel-Crafts alkylation needs an alkyl halide that can give a carbocation. Aryl halides (bromobenz... 1
- In which of the following molecules, all atoms are coplanar? Answer: 4. [structure shown in figure] Key idea: all atoms are coplanar only if every atom is sp2 or sp (no sp3 carbon or its hydrogens). Cy... 1
- Which one of the following structure represents nylon 6,6 polymer? Answer: 3. [structure shown in figure] Key idea: nylon 6,6 is made from hexamethylenediamine and adipic acid, linked by amide bonds. Repeat... 1