Question 1. (b) Select the correct alternative from the choices given: [4 \u00d7 1] (ii) Which, among the following polymers, is a polyester: (iii) The correct order of increasing acidic strength of the oxoacids of chlorine is: (iv) A catalyst is a substance which: (c) Match the following: [4 \u00d7 1]<\/p>\n (d) Answer the following questions: [4 \u00d7 2] (b) (i) \u2192 (2) (c) (i) (d) Question 2. [2] Question 3. [2]<\/p>\n Answer:<\/p>\n Question 4. [2] Question 5. [2]<\/p>\n Answer:<\/p>\n Question 6. [2] Question 7. [2] Question 8. Question 9. [3] Question 10. [3] Question 11. [3] (ii) It reacts with the silver ore, Ag2<\/sub>S, (Argentite) to form soluble complex from which silver can be displaced by adding more electropositive metal like Zn (iii) In the extraction of iron from its oxide, coke acts as Question 12. [3] (ii) (1) x + 6(-1) = -4 \u21d2 x = +2 Question 13. [3] Or Question 14. [3] Question 15. (ii) Electrophoresis: It is the movement of colloidal particles under the influence of the electric field, e.g., when a positive charged ferric hydroxide sol is subjected to an electric field, the colloidal particles migrate towards cathode.<\/p>\n (iii) Dialysis: It is the process of separation of the colloidal particles from those of crystalloids by diffusion of the mixture through a semipermeable membrane e.g., blood is purified in the kidneys because walls of the kidneys are semipermeable.<\/p>\n Question 16. [5] Question 17. [5] (ii) (1) XeF6<\/sub> has distorted octahedral structure (ii) (1) P4<\/sub> + 10H2<\/sub>SO4<\/sub> \u2192 4H3<\/sub>PO4<\/sub> + 10SO2<\/sub> + 4H2<\/sub>O Question 18. [5]
\n(a) Fill in the blanks by choosing the appropriate word\/words from those given in the brackets: [4 \u00d7 1]
\n(more than, primary, cathode, Lucas reagent, two, four, less than, Grignard\u2019s reagent, tertiary, anode, zero, equal to, three)
\n(i) The elevation of a boiling point of 0.5 M K2<\/sub>SO4<\/sub> solution is ……….. that of 0.5 M urea solution. The elevation of the boiling point of 0.5 M KCl solution is …………. that of 0.5 M K2<\/sub>SO4\u00a0<\/sub>solution.
\n(ii) A mixture of conc. HCl and anhydrous ZnCl2<\/sub> is called ……….. which shows maximum reactivity with ……….. alcohol.
\n(iii) In electrolytic refining, the impure metal is made ………. while a thin sheet of pure metal is used as ………..
\n(iv) When the concentration of a reactant of the first-order reaction is doubled, the rate of reaction becomes ………… times, but for a ……… order reaction, the rate of reaction remains the same.<\/p>\n
\n(i) The cell reaction is spontaneous or feasible when emf of the cell is:
\n(1) negative
\n(2) positive
\n(3) zero
\n(4) either positive or negative<\/p>\n
\n(1) melamine
\n(2) bakelite
\n(3) terylene
\n(4) polythene<\/p>\n
\n(1) HCIO3<\/sub> < HClO4<\/sub> < HClO2<\/sub> < HClO
\n(2) HClO < HClO2<\/sub> < HClO3<\/sub> < HClO4<\/sub>
\n(3) HClO2<\/sub> < HClO < HClO4<\/sub> < HClO3<\/sub>
\n(4) HClO3<\/sub> < HClO4<\/sub> < HClO < HClO2<\/sub><\/p>\n
\n(1) changes the equilibrium constant of the reaction
\n(2) increases the equilibrium constant of the reaction
\n(3) supplies energy to the reaction
\n(4) shortens the time to reach equilibrium.<\/p>\n\n\n
\n (i) Diazotisation<\/td>\n (a) Anisotropic<\/td>\n<\/tr>\n \n (ii) Crystalline solid<\/td>\n (b) Reimer-Tiemann reaction<\/td>\n<\/tr>\n \n (iii) Phenol<\/td>\n (c) Diphenyl<\/td>\n<\/tr>\n \n (iv) Fitting reaction<\/td>\n (d) Aniline<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n(i) (1) Which trivalent ion has a maximum size in the Lanthanoid series i.e., Lanthanum ion (La3+<\/sup>) to Lutetium ion (Lu3+<\/sup>)?
\n(at. no. of Lanthanum = 57 and Lutetium = 71)
\n(2) Explain why Cu2+<\/sup> is paramagnetic but Cu+<\/sup> is diamagnetic.
\n(at. no. of Cu = 29)
\n(ii) When a coordination compound C0Cl3<\/sub>.6NH3<\/sub> is mixed with AgNO3<\/sub>, three moles of AgCl are precipitated per mole of the compound. Write the structural formula and IUPAC name of the coordination compound.
\n(iii) Calculate the boiling point of urea solution when 6 g of urea is dissolved in 200 g of water. (Kb<\/sub> for water = 0.52 K kg mol-1<\/sup>, boiling point of pine water = 3 73 K, mol. wt. of urea = 60)
\n(iv) Identify the compounds A, B, C and D in the given reaction:
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-1.png\")
\nAnswer:
\n(a) (i) more than, less than
\n(ii) Lucas reagent, tertiary
\n(iii) anode, cathode
\n(iv) two, zero<\/p>\n
\n(ii) \u2192 (3)
\n(iii) \u2192 (2)
\n(iv) \u2192 (4)<\/p>\n
\n(ii) (a)
\n(iii) (b)
\n(iv) (c)
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-2.png\")
\nCu2+ has one unpaired electron. Therefore, it is paramagnetic. Cu+<\/sup> has no unpaired electrons. Therefore, it is diamagnetic.
\n(ii) [CO(NH3<\/sub>)6<\/sub>]Cl3<\/sub>
\nhexamine cobalt (III) chloride
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-3.png\")
\n(iv) A – CH3<\/sub>CHO, Acetaldehyde
\nB – CH3<\/sub>COOH, Acetic acid
\nC – (CH3<\/sub>COO)2<\/sub>Ca, Calcium acetate
\nD – CH3<\/sub>COCH3<\/sub>, Acetone<\/p>\n
\n(a) For the reaction A + B \u2192 C + D, the initial rate for different reactions and initial concentration of reactants are given below:
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-4.png\")
\n(i) What is the overall order of reaction?
\n(ii) Write the rate law equation.
\nor
\n(b) 25% of a first-order reaction is completed in 30 minutes. Calculate the time taken in minutes for the reaction to go to 90% completion.
\nAnswer:
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-5.png\")
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-6.png\")
<\/p>\n\n
\n
\nFor example phenelzine<\/li>\n<\/ol>\n
\nWrite the balanced chemical equation for each of the following:
\n(i) Chlorobenzene treated with ammonia in the presence of Cu2<\/sub>O at 475 K and 60 atm.
\n(ii) Ethyl chloride treated with alcoholic potassium hydroxide.
\nAnswer:
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-7.png\")
<\/p>\n\n
\n
\nAddition polymerisation<\/li>\n
\nName two water-soluble vitamins and the diseases caused by their deficiency in the diet of an individual.
\nAnswer:
\nTwo water-soluble vitamins are<\/p>\n\n
\n(a) How will you obtain the following? (Give balanced chemical equations):
\n(i) Benzene from phenol.
\n(ii) Iodoform from ethanol.
\nOr
\n(b) How will you obtain the following? (Give balanced chemical equations):
\n(i) Salicylaldehyde from phenol.
\n(ii) Propan-2-ol from Grignard\u2019s reagent.
\nAnswer:
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-8.png\")
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-9.png\")
<\/p>\n
\nShow that for a first-order reaction the time required to complete 75% of reaction is about 2 times more than that required to complete 50% of the reaction.
\nAnswer:
\nFor a first-order reaction
\n\\(t=\\frac{2 \\cdot 303}{k} \\log \\frac{a}{a-x}\\)
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-10.png\")
<\/p>\n
\n(a) When 0.4g of oxalic acid is dissolved in 40g of benzene, the freezing point of the solution is lowered by 0.45 K. Calculate the degree of association of acetic acid. Acetic acid forms dimer when dissolved in benzene.
\n(Kf<\/sub> for benzene = 5.12 K kg mol-1<\/sup>, at. wt. C = 12, H = 1, O = 16)
\nOr
\n(b) A solution is prepared by dissolving 9.25 g of non-volatile solute in 450 mL of water. It has an osmotic pressure of 350 mm of Hg at 27\u00b0C. Assuming the solute is non-electrolyte, determine its molecular mass. (R = 0.0821 lit atm K-1<\/sup> mol-1<\/sup>)
\nAnswer:
\n(a) \u2206Tf<\/sub> = 0.45 K
\ni = ?
\nKf<\/sub> = 5.12 K kg mol-1<\/sup>
\nMB<\/sub> of CH3<\/sub>COOH = 60
\nWA<\/sub> = 40 g
\nWB<\/sub> = 0.4 g
\nWe know that
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-11.png\")
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-12.png\")
<\/p>\n
\nAn element occurs in a body-centred cubic structure. Its density is 8.0 g\/cm3<\/sup>. If the cell edge is 250 pm, calculate the atomic mass of an atom of this element. (N0<\/sub> = 6.023 \u00d7 1023)
\nAnswer:
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-13.png\")
<\/p>\n
\nDescribe the role of the following:
\n(i) Cryolite in the extraction of aluminium from pure alumina.
\n(ii) NaCN in the extraction of silver from silver ore.
\n(iii) Coke in the extraction of iron from its oxides.
\nAnswer:
\n(i) (a) It lowers the melting point of bauxite.
\n(b) It increases the conductivity of the electrolyte.<\/p>\n
\n\\(\\begin{array}{l}{\\mathrm{Ag}_{2} \\mathrm{S}+4 \\mathrm{NaCN}+2 \\mathrm{O}_{2} \\rightleftharpoons 2 \\mathrm{Na}\\left[\\mathrm{Ag}(\\mathrm{CN})_{2}\\right]+\\mathrm{Na}_{2} \\mathrm{SO}_{4}} \\\\ {2 \\mathrm{Na}\\left[\\mathrm{Ag}(\\mathrm{CN})_{2}\\right]+\\mathrm{Zn} \\longrightarrow \\mathrm{Na}_{2}\\left[2 \\mathrm{n}(\\mathrm{CN})_{4}\\right]+2 \\mathrm{Ag} \\downarrow}\\end{array}\\)<\/p>\n
\n(a) fuel
\n(b) Reducing agent<\/p>\n
\n(i) Write the IUPAC names of the following:
\n(1) K3<\/sub>[Fe(C2<\/sub>O4<\/sub>)3<\/sub>]
\n(2) [Co(NH3<\/sub>)5<\/sub>Cl]SO4<\/sub>
\n(ii) [Fe(CN)6<\/sub>]4-<\/sup> is a coordination complex ion.
\n(1) Calculate the oxidation number of iron in the complex.
\n(2) Is the complex ion diamagnetic or paramagnetic?
\n(3) What is the hybridisation state of the central metal atom ?
\n(4) Write the IUPAC name of the complex ion.
\nAnswer:
\n(i) (1) potassium trioxalatoferrate (III)
\n(2) pentaamminechloridocobalt (III) sulphate<\/p>\n
\n(2) Fe2+<\/sup> (3d6<\/sup>) has no unpaired electrons, it is diamagnetic
\n(3) d2<\/sup>sp3<\/sup>
\n(4) hexacyanoferrate (II) ion.<\/p>\n
\n(a) Explain why:
\n(i) Transition elements form alloys.
\n(ii) Zn2+<\/sup> salts are white whereas Cu2+<\/sup> salts are coloured.
\n(iii) Transition metals and their compounds act as a catalyst.
\nOr
\n(b) Complete and balance the following chemical equations:
\n(i) KMnO4<\/sub> + H2<\/sub>SO4<\/sub> + H2<\/sub>C2<\/sub>O4<\/sub> \u2192 ____ + ____ + ____ + _____
\n(ii) K2<\/sub>Cr2<\/sub>O7<\/sub> + H2<\/sub>SO4<\/sub> + KI \u2192 ____ + _____ + _____ + _____
\n(iii) K2<\/sub>Cr2<\/sub>O7<\/sub> + H2<\/sub>SO4<\/sub> + FeSO4<\/sub> \u2192 _____ + _____ + _____ + _____
\nAnswer:
\n(a) (i) This is because transition metals have similar atomic radii and form substitutional alloys.
\n(ii) Zn2+<\/sup>(3d10<\/sup>) salts have no impaired electrons but Cu2-<\/sup>(3d9<\/sup>) salts have one unpaired electrons. Hence Zn2+<\/sup> salts are white while Cu2-<\/sup> salts are coloured.
\n(iii) This is because of transition metals<\/p>\n\n
\n(b) (i) 2KMnO4<\/sub> + 3H2<\/sub>SO4<\/sub> + 5H2<\/sub>C2<\/sub>O4<\/sub> \u2192 K2<\/sub>SO4<\/sub> + 2MnSO4<\/sub> + 8H2<\/sub>O + 10CO2<\/sub>
\n(ii) K2<\/sub>Cr2<\/sub>O7<\/sub> + 7H2<\/sub>SO4<\/sub> + 6KI \u2192 4K2<\/sub>SO4<\/sub> + Cr2<\/sub>(SO4<\/sub>)3<\/sub> + 3I2<\/sub> + 7H2<\/sub>O
\n(iii) K2<\/sub>Cr2<\/sub>O7<\/sub> + 7H2<\/sub>SO4<\/sub> + 6FeSO4<\/sub> \u2192 4K2<\/sub>SO4<\/sub> + Cr2<\/sub>(SO4<\/sub>)3<\/sub> + 3I2<\/sub> + 7H2<\/sub>O<\/p>\n
\nGive balanced equations for the following:
\n(i) Aniline is treated with bromine water.
\n(ii) Ethylamine is heated with chloroform and alcoholic solution of potassium hydroxide.
\n(iii) Benzene diazonium chloride is treated with ice cold solution of aniline in acidic medium.
\nAnswer:
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-14.png\")
<\/p>\n
\nDefine the following terms with suitable examples:
\n(i) Peptisation
\n(ii) Electrophoresis.
\n(iii) Dialysis
\nAnswer:
\n(i) Peptisation: It is the process of conversion of fresh precipitate into colloidal particles by shaking it with dispersion medium in the presence of a small amount of suitable electrolyte.
\ne.g., a reddish-brown coloured colloidal solution is obtained from fresh precipitate of Fe(OH)3<\/sub> by shaking it with a small quantity of a dilute solution of FeCl3<\/sub>.<\/p>\n
\n(a) (i) Calculate the mass of silver deposited at cathode when a current of 2 amperes is passed through a solution of AgNO3<\/sub> for 15 minutes.
\n(at. wt. of Ag= 108, 1F = 96500 C)
\n(ii) Calculate the emf and \u0394G for the cell reaction at 298 K
\nMg(s)|Mg2+<\/sup>(0.1 M) || CU2+<\/sup>(0.01 M)|Cu(s)
\nGiven E\u00b0cell = 2.71 V
\n1F = 96,500 C
\nOr
\n(b) (i) Define the following terms:
\n(1) Specific conductance
\n(2) Kohlrausch\u2019s Law
\n(ii) The resistance of a conductivity cell containing 0.001 M KCl solution at 298 K is 1500 ohm. What is the cell constant and molar conductivity of 0.001 M KCl solution, if the conductivity of this solution is 0.146 \u00d7 10-3<\/sup> ohm-1<\/sup>cm-1<\/sup> at 298 K?
\nAnswer:
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-15.png\")
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-16.png\")
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-17.png\")
\nOr
\n(b) (i) (1) It is the conductivity power of all the ions present in ICC of the solution of the electrolyte.
\n(2) It states that at infinite dilution, the molar conductance of an electrolyte is the sum of molar conductances of its ions with molar conductance of each ion multiplied with the number of ions present in the formula of the electrolyte.
\n(ii) R = 1500 ohms
\nC = 0.001 M
\nk = 0.146 \u00d7 10-3<\/sup> ohm-1<\/sup>cm-1<\/sup>
\nk = conductance \u00d7 cell constant
\n\\(\\begin{aligned} 0.146 \\times 10^{-3} &=\\frac{1}{\\mathrm{R}} \\times \\text { cell constant } \\\\ &=\\frac{1}{1500} \\times \\text { cell constant } \\end{aligned}\\)
\ncell constant = 0.146 \u00d7 10-3<\/sup> \u00d7 1500
\n= 0.146 \u00d7 15 \u00d7 10-1<\/sup>
\n= 0.146 \u00d7 1.5
\ncell constant = 0.2190 ohm-1<\/sup>cm-1<\/sup><\/p>\n
\n(a) (i) Explain why:
\n(1) Fluorine has lower electron affinity than chlorine.
\n(2) Red phosphorus is less reactive than white phosphorus.
\n(3) Ozone acts as a powerful oxidising agent.
\n(ii) Draw the structures of the following :
\n(1) XeF6<\/sub>
\n(2) IF7<\/sub>
\nOr
\n(b) (i) Explain why:
\n(1) Interhalogen compounds are more reactive than the related elemental halogens.
\n(2) Sulphur exhibits tendency for catenation but oxygen does not.
\n(3) On being slowly passed through water, PH3<\/sub> forms bubbles but NH3<\/sub> dissolves.
\n(ii) Complete and balance the following reactions:
\n(1) P4<\/sub> + H2<\/sub>SO4<\/sub> \u2192 ____ + _____ + _____ + _____
\n(2) Ag + HNO3<\/sub>(dilute) \u2192 _____ + ______ + _____ + _____
\nAnswer:
\n(a) (i) F9<\/sub> – 1s2<\/sup>2s2<\/sup>2p5<\/sup>
\nCl17<\/sub> – 1s2<\/sup>2s2<\/sup>2p6<\/sup>3s2<\/sup>3p5<\/sup>
\n(1) This is because in fluorine there is strong electron- electron repulsion for the incoming electron due to the relative compact size of 2p-orbitals in fluorine as compared to 3p-orbitals in chlorine.
\n(2) This is because of in red phosphorus, there are strong covalent bonds in P4<\/sub> molecules but in white phosphorus, there are Van der waals forces of attraction in P4<\/sub> molecules.
\n(3) This is because O3 molecules readily dissociates to give naseent oxygen which oxidises other substances.
\nO3<\/sub> \u2192 O2<\/sub> + [O] Nascent oxygen<\/p>\n
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-18.png\")
\n(2) IF7<\/sub> has the pentagonal bipyramidal structure
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-19.png\")
\nOr
\n(b) (i) (1) This is because these are polar and have lower bond energies.
\n(2) This is because of higher S\u2014S bond energy \\(\\left(\\frac{213 k \\mathrm{J}}{\\mathrm{mol}}\\right)\\) as compared to O-O bond energy \\(\\left(\\frac{138 k \\mathrm{J}}{\\mathrm{mol}}\\right)\\)
\n(3) This is because PH3<\/sub> is insoluble in water (HOH-bonds) but NH3<\/sub> is highly soluble in water due to H-bonds.<\/p>\n
\n(2) 3Ag + 4HNO3<\/sub> \u2192 3AgNO3<\/sub> + NO + 2H2<\/sub>O<\/p>\n
\n(a) (i) Give balanced chemical equations for the following reactions:
\n(1) Acetaldehyde reacts with hydrogen cyanide.
\n(2) Acetone reacts with phenylhydrazine.
\n(3) Acetic acid is treated with ethanol and a drop of conc. H2<\/sub>SO4<\/sub>.
\n(ii) Give one chemical test each to distinguish between the following pairs of compounds:
\n(1) Acetone and benzaldehyde.
\n(2) Phenol and benzoic acid.
\nOr
\n(b) (i) Write chemical equations to illustrate the following name reactions:
\n(1) Aldol condensation.
\n(2) Cannizzaro\u2019s reaction.
\n(3) Benzoin condensation.
\n(ii) Identify the compounds A and B in the given reactions:
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-20.png\")
\nAnswer:
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-21.png\")
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-22.png\")
\n![\"ISC](\"https:\/\/cbselibrary.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2019-Solved-for-Class-12-image-23.png\")
<\/p>\nISC Class 12 Chemistry Previous Year Question Papers<\/a><\/h4>\n","protected":false},"excerpt":{"rendered":"