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22 previous year questions for Chemistry from 3 years. Practice with year-wise breakdown.
22
Questions
3
Years
2
Papers
Complete the following chemical reactions and indicate the category of these reactions. Justify your answer.
(i) 2[Co(CN)5]3− + MeI ⟶
(ii) [Ru(CO)3(PPh3)2] + MeI ⟶
(a) Calculate the ratio of probability of finding the 1s electron of hydrogen atom at r = a0 and at r = 10 a0, where ‘r’ is the distance from the nucleus and a0 = radius of the first Bohr orbit. (b) Construct the Born–Haber cycle for the formation of sodium chloride crystal at 298 K from the elements in their normal states of existence. Mention the names of the involving processes. Indicate which of them are energy demanding and which are energy evolving. (c) Germanium and Silicon elements have very low electrical conductivity. How can the electrical conductivity be enhanced by adding other elements in trace amount? Explain by examples. (d) Two sheets of copper of area 1·50 m2 are separated by 10 cm. What is the rate of transfer of heat by conduction from the warm sheet (50 °C) to the cold sheet (–10 °C)? What is the rate of loss of heat? (Assume the space between the two sheets is filled with air) Given: Coefficient of thermal conductivity of air = 2·4 × 10–2 J s–1 m–1 K–1. (e) Why do liquids become super-heated before boiling? Explain using Kelvin equation. (f) Arrange the following molecules in the ascending order of their dipole moment values. Justify your answer. NH3, NF3 and H2O (g) 0·500 g of benzoic acid was burnt under oxygen. The combustion produced a temperature rise of 1·236 K. The same calorimetric set-up was used to burn 0·300 g of naphthalene and the resulting temperature rise was 1·128 K. The heat of combustion of benzoic acid, ΔcU298 = –3227 kJ mol–1. What is the heat of combustion of naphthalene? (h) A sealed container contains a gaseous sample at 300 K consisting of either pure ethane, or pure neon, or a mixture of the two. The pressure inside the container at this temperature is 1·00 atm. When the container is cooled to 150 K, the pressure is 0·37 atm. What is the composition of the sample; pure ethane, pure neon or a mixture of both? Explain your answer. Given : Vapour pressure of C2H6 at 150 K is 0·10 atm; Critical temperature of neon = 44 K. (i) The surface area of an object to be gold plated is 49·8 cm2, and the density of gold is 19·3 g cm–3. A current of 3·25 A is applied to a solution that contains gold in the +3 oxidation state. Calculate the time required to deposit an even layer of gold, 1 × 10–3 cm thick, on the object. (Given : Molecular mass of gold = 196·97 g mol–1) (j) A steam turbine is operated with an intake temperature of 400 °C, and an exhaust temperature of 150 °C. What is the maximum amount of work the turbine can do for a given heat input ‘Q’? Under what conditions is the maximum work achieved?
(a) Calculate the ratio of probability of finding the 1s electron of hydrogen atom at r = a0 and at r = 10 a0, where ‘r’ is the distance from the nucleus and a0 = radius of the first Bohr orbit. [5M]
(b) Construct the Born–Haber cycle for the formation of sodium chloride crystal at 298 K from the elements in their normal states of existence. Mention the names of the involving processes. Indicate which of them are energy demanding and which are energy evolving. [5M]
(c) Germanium and Silicon elements have very low electrical conductivity. How can the electrical conductivity be enhanced by adding other elements in trace amount? Explain by examples. [5M]
(d) Two sheets of copper of area 1·50 m2 are separated by 10 cm. What is the rate of transfer of heat by conduction from the warm sheet (50 °C) to the cold sheet (–10 °C)? What is the rate of loss of heat? (Assume the space between the two sheets is filled with air) Given: Coefficient of thermal conductivity of air = 2·4 × 10–2 J s–1 m–1 K–1. [5M]
(e) Why do liquids become super-heated before boiling? Explain using Kelvin equation. [5M]
(f) Arrange the following molecules in the ascending order of their dipole moment values. Justify your answer. NH3, NF3 and H2O [5M]
(g) 0·500 g of benzoic acid was burnt under oxygen. The combustion produced a temperature rise of 1·236 K. The same calorimetric set-up was used to burn 0·300 g of naphthalene and the resulting temperature rise was 1·128 K. The heat of combustion of benzoic acid, ΔcU298 = –3227 kJ mol–1. What is the heat of combustion of naphthalene? [5M]
(h) A sealed container contains a gaseous sample at 300 K consisting of either pure ethane, or pure neon, or a mixture of the two. The pressure inside the container at this temperature is 1·00 atm. When the container is cooled to 150 K, the pressure is 0·37 atm. What is the composition of the sample; pure ethane, pure neon or a mixture of both? Explain your answer. Given : Vapour pressure of C2H6 at 150 K is 0·10 atm; Critical temperature of neon = 44 K. [5M]
(i) The surface area of an object to be gold plated is 49·8 cm2, and the density of gold is 19·3 g cm–3. A current of 3·25 A is applied to a solution that contains gold in the +3 oxidation state. Calculate the time required to deposit an even layer of gold, 1 × 10–3 cm thick, on the object. (Given : Molecular mass of gold = 196·97 g mol–1) [5M]
(j) A steam turbine is operated with an intake temperature of 400 °C, and an exhaust temperature of 150 °C. What is the maximum amount of work the turbine can do for a given heat input ‘Q’? Under what conditions is the maximum work achieved? [5M]
Answer the following sub-parts:
(a) (i) Tropolone is aromatic, but fulvene is non-aromatic. Why? (ii) Explain with an example pseudo-aromaticity. [10M]
(b) Identify the missing reagent and intermediates in the following chemical conversion. [Structures as shown in the paper] [10M]
(c) Write the structure of the major product when neopentyl chloride is reacted with sodium ethoxide in ethanol. Justify your answer. [10M]
(d) (i) Discuss in detail how the reaction of a carbene with cis-2-butene can be used to define the spin state (S/T) of a carbene. (ii) para-Bromophenol on reaction with NaNH2 / NH3 (l) followed by acidic work-up yields one major product. Explain the reaction by writing the steps involved. [10M]
(e) With example, elucidate the permanent and temporary denaturation of a protein. [10M]
(a) Find the probability of existence of a particle in a one-dimensional box of length ‘a’ in the region 0 ≤ x ≤ a⁄4 for the states n = 1, 2 and 3. (b) The standard reduction potential of oxygen under acidic conditions at 298 K is +1·23 V. What is the standard reduction potential for the four-electron reduction of O2(g) under basic conditions? (c) The radii of Zn2+ and S2– ions are 0·74 Å and 1·84 Å respectively. Determine the most stable form of arrangement of ions in ZnS crystal lattice. Draw the CCP (Cubic Close Packing) structure of ZnS. (d) In a sample of NaCl, one of every 10,000 sites, normally occupied by Na+, is occupied instead by Ca2+. Assuming that all of the Cl– sites are fully occupied, what is the stoichiometry of the sample?
(a) Find the probability of existence of a particle in a one-dimensional box of length ‘a’ in the region 0 ≤ x ≤ a⁄4 for the states n = 1, 2 and 3. [15M]
(b) The standard reduction potential of oxygen under acidic conditions at 298 K is +1·23 V. What is the standard reduction potential for the four-electron reduction of O2(g) under basic conditions? [15M]
(c) The radii of Zn2+ and S2– ions are 0·74 Å and 1·84 Å respectively. Determine the most stable form of arrangement of ions in ZnS crystal lattice. Draw the CCP (Cubic Close Packing) structure of ZnS. [15M]
(d) In a sample of NaCl, one of every 10,000 sites, normally occupied by Na+, is occupied instead by Ca2+. Assuming that all of the Cl– sites are fully occupied, what is the stoichiometry of the sample? [5M]
Answer the following sub-parts:
(a) (i) In the presence of sodium ethoxide, the following transformation occurs. Explain. [Structures as given] (ii) Propose a suitable mechanism for the following transformation. [Structures as given] [15M]
(b(i)) The following reaction does not produce the product shown. [Reaction scheme given] (1) Predict the major product from the conditions shown above and write a detailed mechanism for its formation. (2) Write the reaction conditions which would lead to successful synthesis of the product shown above (i.e., 3,3-dimethyl-2-butanol). [10M]
(b(ii)) Write the structure of the major product(s) formed in the following reaction. Justify your answer. Ph —BrCCl3, hν → ? [5M]
(c) Write the structure of the major product(s) formed in each of the following reactions: (i) 1) KOH 2) HA → ? (ii) (H⁺) → ? (iii) 1) NH2OH 2) Al2O3 → ? (iv) –OEt → ? [20M]
(a) Calculate the number of collisions that oxygen makes per second on 1·00 cm2 of the surface of the vessel containing them if the pressure is 1·00 × 10–6 atm and the temperature is 25 °C. (b) Suppose that 10·0 J of work is required to create droplets of uniform size from a mole of water in bulk at 25 °C and 1 atm pressure. (i) Assuming that surface tension is independent of area, calculate the radius of the droplets. (ii) Calculate the number of water molecules in a droplet. Given : Surface tension of water = 0·072 J m–2
(a) Calculate the number of collisions that oxygen makes per second on 1·00 cm2 of the surface of the vessel containing them if the pressure is 1·00 × 10–6 atm and the temperature is 25 °C. [10M]
(b) Suppose that 10·0 J of work is required to create droplets of uniform size from a mole of water in bulk at 25 °C and 1 atm pressure. (i) Assuming that surface tension is independent of area, calculate the radius of the droplets. (ii) Calculate the number of water molecules in a droplet. Given : Surface tension of water = 0·072 J m–2. [15M]
Answer the following sub-parts:
(a(i)) Write the structure of the product formed in the following reactions: (1) (bromocyclohexanone with MeO−); (2) Ethoxycarbonyl-sulfonamide system in the presence of NEt3. [Reaction schemes as shown] [10M]
(a(ii)) Describe the synthesis of ketone (A) when only isobutanol is available as the starting material. [5M]
(b(i)) Write the steps involved in the following conversion: ClCO2tBu → (cyclopropane dicarboxylate) under tBuOK. [Scheme as shown] [10M]
(b(ii)) Elucidate the structure of compounds C and D in the following conversion involving ozonolysis followed by hydrogenation. [Scheme as shown] [5M]
(c) In the following transformation give the missing reagent and intermediates (M, N, O, P) leading to the formation of the final product shown. [Reaction scheme with HO-CH2CH2CH3 → … → OHNH2] [20M]
(a) (i) After polymerization of p-hydroxybenzoic acid, IR analysis shows 0·2 % unreacted —COOH. Calculate the molecular weight of the polymer and categorize it. (ii) Write the structure of the polymer formed when p-hydroxybenzoic acid is polymerized. (iii) What is the precursor of the main component of natural rubber? Draw the structures of both monomer and polymer. (b) (i) Compare the salient properties of Nylon 6 and Nylon 6,6. (ii) How would you prepare syndiotactic polystyrene? (iii) What are the salient features of alpha helix in regards to handedness, residues per turn and elongation per residue? What are the principal stabilizing factors for an alpha helix? (c) (i) Compounds 1 and 2 on reaction with NaN3 yield the same product but compound 1 reacts at room temperature while compound 2 reacts at 200 °C. Identify the product formed and explain the reasons for different reactivities of compounds 1 and 2. (ii) Identify the major product in the following reactions and justify your answer.
(a(i)) After polymerization of p-hydroxybenzoic acid, IR analysis shows 0·2 % unreacted —COOH. Calculate the molecular weight of the polymer and categorize it. [7M]
(a(ii)) Write the structure of the polymer formed when p-hydroxybenzoic acid is polymerized. [3M]
(a(iii)) What is the precursor of the main component of natural rubber? Draw the structures of both monomer and polymer. [5M]
(b(i)) Compare the salient properties of Nylon 6 and Nylon 6,6. [5M]
(b(ii)) How would you prepare syndiotactic polystyrene? [5M]
(b(iii)) What are the salient features of alpha helix in regards to handedness, residues per turn and elongation per residue? What are the principal stabilizing factors for an alpha helix? [5M]
(c(i)) Compounds 1 and 2 on reaction with NaN3 yield the same product, but compound 1 reacts at room temperature while compound 2 reacts at 200 °C. Identify the product formed and explain the reasons for the different reactivities of compounds 1 and 2. [10M]
(c(ii)) Identify the major product in the following reactions and justify your answer. [10M]
(a) Write the structure of the product(s) and the intermediate formed in the following reaction. (b) Deduce the structure of the starting material (A) and all the intermediates formed in each step that would lead to the formation of the given product through the defined reactions. (c) A photochemical reaction takes place through the T1 state. S0–S1 and S0–T1 energy gaps correspond to 290 nm and 450 nm, respectively. To get an efficient photochemical reaction should we use light of 290 nm or 450 nm? Give your answer presenting the relevant Jablonski diagram. (d) (i) Which of the following molecules is/are active to rotational spectroscopy and why? CH4, H2O, NH3, BCl3, XeF4. (ii) The spacing between lines in the microwave spectrum of CO decreases by substituting 12C by 13C. Why? (e) (i) In a 100 MHz NMR instrument, a particular set of protons absorbs at δ = 3·0 with J = 4·5 Hz. Find the chemical shift (in Hz) and the coupling constant J in a 500 MHz instrument for the same set of protons. (ii) The mass spectrum of n-butyl phenyl ketone (C6H5COCH2CH2CH2CH3) shows peaks at m/z 162, 120, 105 and 85. Predict the fragmentation pattern.
(a) Write the structure of the product(s) and the intermediate formed in the given reaction. [10M]
(b) Deduce the structure of the starting material (A) and all the intermediates that lead to the stated product through the defined reactions. [10M]
(c) Discuss whether light of 290 nm or 450 nm should be used for an efficient photochemical reaction, supporting your answer with a Jablonski diagram. [10M]
(d(i)) Which of the following molecules is/are active to rotational spectroscopy and why? CH4, H2O, NH3, BCl3, XeF4. [5M]
(d(ii)) Explain why the spacing between lines in the microwave spectrum of CO decreases on substituting 12C by 13C. [5M]
(e(i)) For protons absorbing at δ = 3·0 with J = 4·5 Hz on a 100 MHz NMR instrument, calculate the chemical shift in Hz and the coupling constant J on a 500 MHz instrument. [5M]
(e(ii)) Predict the fragmentation pattern corresponding to the peaks at m/z 162, 120, 105 and 85 in the mass spectrum of n-butyl phenyl ketone (C6H5COCH2CH2CH2CH3). [5M]
(a) (i) Elucidate the structure of the product and the intermediate (if any) in the following reactions. (ii) Describe the role of N-methylmorpholine N-oxide (NMO) during the dihydroxylation of an alkene using catalytic OsO4. (b) (i) Calculate the frequency of radiation required for a transition of J = 4 to J = 5 in the rotational spectrum of HCl. (B = 10·6 cm⁻¹) (ii) The fundamental vibrational frequency of HCl is 2990 cm⁻¹. Calculate the corresponding frequency for DCl assuming the same bond strength. (iii) A compound has molecular formula C3H3N. Its IR absorptions are 1650 cm⁻¹, 2250 cm⁻¹ and 3100 cm⁻¹. Assign a structure. (c) (i) Write the mechanism for the following photochemical transformation. (ii) Photobromination of cinnamic acid was carried out with 480 nm light of intensity 1·5 × 10⁻³ J s⁻¹ for 10 min causing a decrease of 0·05 mmol of Br2. Calculate the quantum yield assuming 80 % radiation absorption (h = 6·627 × 10⁻³⁴ J s, c = 3 × 10⁸ m s⁻¹). (iii) Predict the major and minor products for the given photoreaction and give the logic. (iv) Assign A, B and C in the following reaction.
(a(i)) Elucidate the structure of the product and any intermediate formed in the given reactions. [10M]
(a(ii)) Describe the role of N-methylmorpholine N-oxide (NMO) during OsO4-catalysed dihydroxylation of an alkene. [5M]
(b(i)) Calculate the frequency for the J = 4 → J = 5 transition in the rotational spectrum of HCl (B = 10·6 cm⁻¹). [5M]
(b(ii)) Given ν₀(HCl) = 2990 cm⁻¹, calculate the fundamental vibrational frequency of DCl. [5M]
(b(iii)) Assign a structure to a compound of formula C3H3N with IR absorptions at 1650 cm⁻¹, 2250 cm⁻¹ and 3100 cm⁻¹. [5M]
(c(i)) Write the mechanism for the specified photochemical transformation. [5M]
(c(ii)) Calculate the quantum yield for photobromination of cinnamic acid under the given conditions. [5M]
(c(iii)) Predict the major and minor products for the stated photoreaction, giving reasons. [5M]
(c(iv)) Assign species A, B and C in the given reaction. [5M]
(a) (i) Acetone shows a weak absorption at 280 nm and a strong absorption at 190 nm in the UV spectrum. Account for the observation. (ii) Using Woodward–Fieser rules, calculate λmax for the following compounds (structures A, B, C and D are provided).
(a(i)) Explain why acetone exhibits weak absorption at 280 nm but strong absorption at 190 nm in its UV spectrum. [5M]
(a(ii)) Using Woodward–Fieser rules, calculate λmax for the given compounds A, B, C and D. [5M]
8. (a) (i) Estimate the expected splitting (coupling constant J in Hz) for the lettered protons in the 1H NMR spectrum of the following compounds : (1) CH2Br-CH2Cl, (2) Cl-CH2-CH2-Cl, (3) Ha-C≡C-CH2-Cl. (ii) Compare the chemical shifts of the labelled protons Ha and Hb in the 1H NMR spectrum of the following compounds and justify your answer : (D) Ha-CH2-OCH3, (E) Hb-CH2-OCOCH3. (iii) Count the number of peaks observed in the 1H NMR spectrum of the following compounds. Justify your answer : (1) CH3-CH2-CH2-Cl, (2) (CH3)3C-Cl. (b) (i) A halogenated ester shows M+ peak at m/z 166 (10 %) and M+2 peak at m/z 168 (9·8 %) in mass spectrum. 1H NMR spectrum of this compound shows two triplets and a singlet at δ 2·9, 3·6 and 3·8 ppm, respectively, in the intensity ratio 1 : 1 : 1·5. Deduce the structure of the compound. Justify your answer. (ii) Two isomeric alkenes with same molecular formula C6H12 show strong peaks at m/z 42 and 56 in the mass spectrum. Propose fragmentation pattern for both the peaks. (c) (i) (1) Phthalic acid diethyl ester shows a characteristic peak at m/z 149 in the mass spectrum. Account for the observance of this peak by fragmentation pattern. (2) The mass spectrum of ethylbenzene shows a characteristic peak at m/z 91 while n-propylbenzene shows strong peak at m/z 92. Explain with the help of fragmentation pattern. (ii) An unknown organic compound with molecular formula C4H5NO2 displays a band at 2250 cm−1 and a strong band at 1740 cm−1 in the IR spectrum. The compound shows only two signals in 3 : 2 ratio in the 1H NMR spectrum. Find out the structure of the compound. Justify your answer.
(a(i)) Estimate the expected splitting (coupling constant J in Hz) for the lettered protons in the 1H NMR spectrum of the given compounds. [5M]
(a(ii)) Compare the chemical shifts of the labelled protons Ha and Hb in the 1H NMR spectrum of the given compounds and justify your answer. [10M]
(a(iii)) Count the number of peaks observed in the 1H NMR spectrum of the given compounds. Justify your answer. [5M]
(b(i)) A halogenated ester shows M+ peak at m/z 166 (10 %) and M+2 peak at m/z 168 (9·8 %) in mass spectrum. 1H NMR spectrum shows two triplets and a singlet at δ 2·9, 3·6 and 3·8 ppm, respectively, in the intensity ratio 1 : 1 : 1·5. Deduce the structure of the compound and justify your answer. [10M]
(b(ii)) Two isomeric alkenes with molecular formula C6H12 show strong peaks at m/z 42 and 56 in the mass spectrum. Propose fragmentation pattern for both the peaks. [5M]
(c(i)) (1) Phthalic acid diethyl ester shows a characteristic peak at m/z 149 in the mass spectrum. Account for this peak with the help of fragmentation pattern. (2) Ethylbenzene shows a characteristic peak at m/z 91 while n-propylbenzene shows a strong peak at m/z 92. Explain with the help of fragmentation pattern. [10M]
(c(ii)) An unknown organic compound (C4H5NO2) shows a band at 2250 cm−1 and a strong band at 1740 cm−1 in its IR spectrum. It displays only two signals in the 1H NMR spectrum in 3 : 2 ratio. Determine the structure of the compound and justify your answer. [10M]
(a) (i) Determine the distance from the nucleus at which the electron is most expected in the hydrogen atom in its ground state. [Given: The normalised radial function for hydrogen-like systems is R10(1s) = 2 (Z/a0)3/2 e−ρ/2 where ρ = 2Zr/na0 and a0 is the first Bohr orbit radius. Other notations have their usual meanings.] (ii) Sodium bromide and sodium iodide have higher lattice energies than expected from theoretical calculations. Justify. (b) (i) The 235U isotope undergoes fission when bombarded with neutrons. However, its natural abundance is only 0·72 percent. To separate it from more abundant 238U isotope, U is first converted to UF6 which is easily vaporised above room temperature. The mixture of 235UF6 and 238UF6 gases is then subjected to many stages of effusion. Calculate the separation factor, that is enrichment of 235U relative to 238U after one stage of effusion. (ii) Define ‘unit cell’. Draw all the Bravais lattices for a cubic system. (c) Use the following data to determine the normal boiling point of mercury. What assumptions must you make in order to do the calculations? Hg(l) ΔHf° = 0, S° = 77·4 J K−1 mol−1 Hg(g) ΔHf° = 60·78 kJ mol−1, S° = 174·7 J K−1 mol−1 (d) (i) The compound dichlorodifluoromethane (CCl2F2) has a normal boiling point of –30 °C, a critical temperature of 112 °C, and a corresponding critical pressure of 40 atm. If the gas is compressed to 18 atm at 20 °C, will the gas condense? Give your answer on the basis of graphical presentation. (ii) Define overvoltage. Mention the applications of overvoltage. (e) The activation energy for the decomposition of hydrogen peroxide 2 H2O2(aq) → 2 H2O(l) + O2(g) is 42 kJ mol−1, whereas when the reaction is catalysed by enzyme catalase it is 7·0 kJ mol−1. Calculate the temperature that would cause the uncatalysed reaction to proceed as rapidly as the enzyme-catalysed decomposition at 20 °C. Assume the frequency factor A to be the same in both cases.
(a(i)) Determine the distance from the nucleus at which the electron is most expected in the hydrogen atom in its ground state. [5M]
(a(ii)) Sodium bromide and sodium iodide have higher lattice energies than expected from theoretical calculations. Justify. [5M]
(b(i)) Calculate the separation factor (enrichment of 235U relative to 238U) after one stage of effusion of a UF6 gas mixture. [5M]
(b(ii)) Define ‘unit cell’. Draw all the Bravais lattices for a cubic system. [5M]
(c) Using the given thermodynamic data, determine the normal boiling point of mercury and state the assumptions involved. [10M]
(d(i)) Will CCl2F2 gas condense when compressed to 18 atm at 20 °C? Give your answer on the basis of graphical presentation. [5M]
(d(ii)) Define overvoltage and mention its applications. [5M]
(e) Calculate the temperature at which the uncatalysed decomposition of H2O2 will proceed as rapidly as the enzyme-catalysed reaction at 20 °C, assuming identical frequency factors. [10M]
Answer ALL the parts (a) to (e):
(a(i)) Classify the following as aromatic, nonaromatic or antiaromatic: (1) Azulene (2) Pyridine (3) Sydnone (4) Cyclooctatetraene (5) Cyclopentadienyl cation [5M]
(a(ii)) Though the following compound contains a keto group, it does not undergo nucleophilic addition reactions. Explain. [5M]
(b) What is the intermediate formed during the following reaction? (Reaction: C6H5-CH2-Br + ⁻NH2 → C6H5-NH2 ) Explain any one experimental proof for the formation of the intermediate. [10M]
(c) How is the following conversion brought about? (S)-2-Butanol → (S)-2-Butyl chloride Explain its mechanism. [10M]
(d) Write the name of the reaction and the reagent required for each of the following conversions: (i) to (v) as shown in the paper. [10M]
(e) Consider the following electrocyclic reactions: I step 100 °C II step hν ➝ M III step 25 °C (i) Predict the mode of ring closure/opening at each of the three steps. (ii) Predict the structure of M. (iii) Are the indicated hydrogens cis or trans? [10M]
(a) State Heisenberg’s uncertainty principle. Show that for a particle in a one-dimensional box having length from 0 to L, the two normalised eigen functions corresponding to the eigenvalues E1 and E2 (quantum numbers 1 and 2 respectively) are orthogonal to each other. (b) (i) Calculate the bond order for the following: (I) Oxygen, (II) Superoxide, (III) Peroxide, (IV) Dioxygenyl ion. Which of them has the highest stability? (ii) Draw the molecular orbital diagram for CO. (c) (i) Calculate the limiting radius ratio for crystals with coordination numbers 3 and 6. (ii) Explain stoichiometric defects with an example.
(a) State Heisenberg’s uncertainty principle and prove orthogonality of the first two eigen functions for a particle in a one-dimensional box. [10M]
(b(i)) Calculate bond orders for O2, O2− (superoxide), O22− (peroxide) and O2+ (dioxygenyl) and identify the most stable species. [10M]
(b(ii)) Draw the molecular orbital diagram for CO. [10M]
(c(i)) Calculate the limiting radius ratio for coordination numbers 3 and 6. [10M]
(c(ii)) Explain stoichiometric defects with an example. [10M]
Answer the following:
(a(i)) Consider the following reactions: C6H5-CH2-CH2-Br + EtO⁻ → C6H5-CH=CH2 (Rate = k_H) C6H5-CD2-CD2-Br + EtO⁻ → C6H5-CH=CHD (Rate = k_D) It was observed that k_H / k_D = 7.1. Based on this data, predict the mechanism and justify your answer. [10M]
(a(ii)) Consider the following reaction: CH2=CH-CH=CH2 + HBr → CH3-CH(Br)-CH=CH2 + CH3-CH=CH-CH2Br At −80 °C, the 1,2-addition product predominates while at −45 °C the 1,4-addition product predominates. Justify. [5M]
(b(i)) Identify the major product X in the following reaction, explain its mechanism and name the reaction: C6H5-CHO + CH2(COOC2H5)2 (pyridine) → X [10M]
(b(ii)) Predict the structure of X in the following reaction and name the reaction. Justify that it is a syn-elimination: tert-Butyl alcohol (with CS2, NaOH; then CH3I) → X → (elimination product) [5M]
(a) (i) Calculate the coefficient of viscosity of air at (I) 298 K and (II) 0 K. Assume that the collision cross-section (πσ2) of air is 0·28 (nm)2 and the average molar mass of air is 29 g mol−1. (ii) Arrange Boyle’s temperatures of the gases Ar, CH4 and C6H6 in increasing order and give reasons. (b) (i) Which of the following liquids has greater surface tension: Ethanol or Dimethyl ether? Explain with reasons. (ii) Calculate the difference in pressure across the liquid–air interface for a water droplet of radius 150 nm. (c) (i) Calculate the change in Helmholtz energy for a reversible isothermal compression of 1 mol of an ideal gas from 100·0 L to 22·4 L at 298 K. (ii) Why does a tyre get hot when air is pumped into it? Can a tyre be inflated without a rise in temperature?
(a(i)) Calculate the coefficient of viscosity of air at 298 K and 0 K. [10M]
(a(ii)) Arrange Boyle’s temperatures of Ar, CH4 and C6H6 in increasing order and justify. [5M]
(b(i)) Identify which liquid—ethanol or dimethyl ether—has the greater surface tension and explain. [5M]
(b(ii)) Calculate the pressure difference across the liquid–air interface of a water droplet (radius 150 nm). [5M]
(c(i)) Determine the change in Helmholtz energy for isothermal compression of an ideal gas from 100 L to 22·4 L at 298 K. [10M]
(c(ii)) Explain why a tyre gets hot during inflation and whether it can be inflated without a temperature rise. [5M]
The mass spectral data of diethyl ether is as under: m/z 74, m/z 59, m/z 45, m/z 31, m/z 29. Explain the fragmentation pattern.
Using the following data, calculate the bond length of HCl : I = 2.70 × 10^−47 kg m^2 ; 1 a.m.u. = 1.661 × 10^−27 kg.
Consider the reaction H2(g) + 1/2 O2(g) → H2O(l), which occurs in a H2–O2 fuel cell. (i) Identify the elements that undergo oxidation and reduction. (ii) Calculate the standard reaction Gibbs free energy (ΔrG°) at 25 °C. (iii) Write down the two reduction half-reactions for the cell. (iv) Calculate the Ecell. Given that ΔfH°(H2O, l) = –285.83 kJ mol–1 Sm°(H2O, l) = 69.91 J K–1 mol–1 Sm°(H2, g) = 130.68 J K–1 mol–1 Sm°(O2, g) = 205.14 J K–1 mol–1
Identify all the possible products in the above reaction showing the sequential pathways of their formation.
For the following compound : (i) Identify the site of initial ionization under EI conditions. (ii) Draw the structure of ion having m/z = 58 value. (iii) Calculate the m/z value of metastable ion formed during the formation of the above ion.
(i) Identify the site of initial ionization under EI conditions.
(ii) Draw the structure of ion having m/z = 58 value.
(iii) Calculate the m/z value of metastable ion formed during the formation of the above ion.
We have 22 UPSC Mains Chemistry optional subject questions spanning 3 years (2023–2025).
Chemistry has 2 papers in UPSC Mains: Chemistry-I, Chemistry-II. Each paper carries 250 marks.