Chemistry
- Which of the following oxoacid of sulphur has -O-O- linkage ? Answer: 3. H ₂ S ₂ O ₈ , peroxodisulphuric acid The peroxo linkage -O-O- is present in peroxoacids. H₂S₂O₈ (peroxodisulphuric acid, Marshall... 1
- On electrolysis of dil.sulphuric acid using Platinum (Pt) electrode, the product obtained at anode will be : Answer: 2. Oxygen gas In dilute H₂SO₄ with inert Pt electrodes, water is oxidised at the anode more easily than the sulphate ion. Anode: 2H₂... 1
- Which of the following series of transitions in the spectrum of hydrogen atom falls in visible region ? Answer: 2. Balmer series Balmer series (transitions to n = 2 from n = 3, 4, 5...) lies in the visible region (about 656 to 365 nm). Lyman is... 1
- Among the following, the narrow spectrum antibiotic is : Answer: 1. penicillin G Narrow spectrum antibiotics act on a limited range of bacteria. Penicillin G is mainly effective against gram-positi... 1
- A compound is formed by cation C and anion A. The anions form hexagonal close packed (hcp) lattice and the cations occupy 75% of octahedral voids. The formula of the compound is : Answer: 3. C ₃ A ₄ In hcp, if there are N anions then there are N octahedral voids. Cations occupy 75% of octahedral voids, so cations = 0.7... 1
- For the chemical reactionN_2(g) + 3H_2(g) ⇌ 2NH_3(g)the correct option is : Answer: 3. -d[N₂]/dt = 1/2d[NH₃]/dt Rate of reaction: divide the rate of change of each species by its stoichiometric coefficient (negative... 1
- In which case change in entropy is negative ? Answer: 4. 2H(g) → H ₂ (g) Entropy measures disorder. Evaporation, sublimation and isothermal expansion all increase randomness ( Δ S>0 ). I... 1
- Which of the following is an amphoteric hydroxide ? Answer: 4. Be(OH) ₂ Going down group 2, hydroxides become more basic. Sr(OH)₂ , Ca(OH)₂ and Mg(OH)₂ are basic. Be(OH)₂ dissolves in both aci... 1
- The method used to remove temporary hardness of water is : Answer: 2. Clark's method Key idea: temporary hardness is due to bicarbonates of Ca and Mg, and the method meant specifically for it is Clar... 1
- What is the correct electronic configuration of the central atom in K_4[Fe(CN)_6] based on crystal field theory ? Answer: 2. t_2g⁶e_g⁰ In K₄[Fe(CN)₆] iron is Fe(II), a d⁶ ion. CN^- is a strong field ligand, so the pairing energy is lower than Δ_o and all... 1
- The manganate and permanganate ions are tetrahedral, due to : Answer: 1. The π -bonding involves overlap of p-orbitals of oxygen with d-orbitals of manganese In MnO₄^- and mathrmMnO₄²⁻ , Mn uses sp³ hyb... 1
- Which one is malachite from the following ? Answer: 4. CuCO ₃ .Cu(OH) ₂ Malachite is the green basic copper carbonate CuCO₃· Cu(OH)₂ . CuFeS₂ is copper pyrites and Fe₃O₄ is magnetite.... 1
- Which will make basic buffer ? Answer: 3. 100 mL of 0.1 M HCl + 200 mL of 0.1 M NH ₄ OH A basic buffer is a weak base plus its salt (conjugate acid). (1) 5 mmol NaOH + 2.5... 1
- Conjugate base for Brönsted acids H_2O and HF are : Answer: 3. OH ^- and F ^- , respectively A conjugate base is formed when the acid loses H^+ . H₂O → OH^- + H^+ and HF → F^- + H^+ . So the c... 1
- An alkene "A" on reaction with O_3 and Zn-H_2O gives propanone and ethanal in equimolar ratio. Addition of HCl to alkene "A" gives "B" as the major product. The structure of product "B" is : Answer: 3. H ₃ C-CH ₂ -C(CH ₃ )(Cl)-CH ₃ (see figure) Work back from the ozonolysis products. Propanone (CH₃)₂C=O and ethanal CH₃CHO join at... 1
- Among the following, the reaction that proceeds through an electrophilic substitution, is : Answer: 2. (structure 2, see figure): benzene + Cl ₂ xrightarrowAlCl₃ chlorobenzene + HCl (1) Sandmeyer reaction: via aryl radical / diazoni... 1
- The correct order of the basic strength of methyl substituted amines in aqueous solution is : Answer: 1. (CH₃)₂NH > CH₃NH₂ > (CH₃)₃N In aqueous solution basicity depends on both the inductive effect (more alkyl groups push electrons)... 1
- The major product of the following reaction is :phthalic acid (benzene-1,2-dicarboxylic acid) + NH_3 strong\ heating Answer: 2. phthalimide (see figure) Phthalic acid reacts with ammonia to give the ammonium salt; strong heating removes water in two steps (... 1
- The compound that is most difficult to protonate is : Answer: 4. Ph-O-H Protonation occurs on the oxygen lone pair; the more available the lone pair, the easier it is to protonate. H₂O , CH₃OH ,... 1
- Which of the following species is not stable ? Answer: 4. [SiCl₆]²⁻ Key idea: silicon (period 3) can expand its octahedral coordination, but only with small ligands. mathrm[SiF₆]²⁻ is kno... 1
- Identify the incorrect statement related to PCl_5 from the following : Answer: 4. PCl ₅ molecule is non-reactive PCl₅ is trigonal bipyramidal. Three equatorial P-Cl bonds are at 120 to each other: correct. Two a... 1
- Match the Xenon compounds in Column - I with its structure in Column - II and assign the correct code :Column - I: (a) XeF_4 (b) XeF_6 (c) XeOF_4 (d) XeO_3Column - II: (i) pyramidal (ii) square planar (iii) distorted octahedral (iv) square pyramidalC… Answer: 2. (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i) (a) XeF₄ : square planar, (ii) (b) XeF₆ : distorted octahedral, (iii) (c) XeOF₄ : square p... 1
- Which mixture of the solutions will lead to the formation of negatively charged colloidal [AgI]I^- sol. ? Answer: 1. 50 mL of 1 M AgNO ₃ + 50 mL of 1.5 M KI or 2. 50 mL of 1 M AgNO ₃ + 50 mL of 2 M KI In the sol [AgI]I^- , AgI adsorbs the common... 1
- For a cell involving one electron E^_cell = 0.59 V at 298 K, the equilibrium constant for the cell reaction is :[Given that 2.303 RT/F = 0.059 V at T = 298 K] Answer: 3. 1.0×10¹⁰ At 298 K, E^(ominus)_cell = 0.059/nlog K . log K = dfracnE^(ominus)0.059 = 1×0.59/0.059 = 10 , so K = 1.0×10¹⁰ . Option... 1