\nGas constant R = 1.987 cal deg-1<\/sup> mol-1<\/sup> = 8.314 JK-1<\/sup> mol-1<\/sup> = 0.0821 dm3<\/sup> atm K-1<\/sup> mol-1<\/sup>. 1 L atm = 1 dm3<\/sup> atm = 101.3 J.
\n1 Faraday = 96500 Coulombs, Avogadro\u2019s number = 6.023 \u00d7 1023<\/sup><\/li>\n<\/ul>\n
Part – I (20 Marks)<\/strong> Question 1. (b) Complete the following statements by selecting the correct alternative from the choices given: [5] (ii) The complexion [Ni(CN)4<\/sub>]2-<\/sup> is: (iii) Wohler\u2019s synthesis is used for the preparation of: (iv) When SO2<\/sub> gas is passed through the acidified K2<\/sub>Cr2<\/sub>O7<\/sub> solution, the colour of the solution changes to: (v) In the equation \\(\\mathrm{CH}_{3} \\mathrm{COOH}+\\mathrm{Cl}_{2} \\frac{\\mathrm{Red} P}{-\\mathrm{HCl}} \\mathrm{A}\\), the compound A is: (c) Answer the following questions: [5] (d) Match the following: [5]<\/p>\n Answer: (b) (i) -1 Part – II (50 Marks)<\/strong><\/p>\n A nswer six questions choosing two from Section A, two from Section B and two from Section C.<\/p>\n Section – A<\/strong> Question 2. Question 3. Question 4. (a) Suppose a few drops of HCl are added to the buffer. Here H+<\/sup> ions from HCl will combine with OH–<\/sup> ions from NH4<\/sub>OH to form unionised water molecules. (b) Suppose a few drops of NaOH are added to the buffer. Here OH–<\/sup> ions from NaOH combine with NH4+<\/sup> ions from NH4<\/sub>Cl to give weakly ionised NH4<\/sub>OH molecules. (c) Suppose the buffer solution is diluted with water, it will not change the pH of the solution because the concentration of H+<\/sup> and OH–<\/sup> ions remains unchanged.<\/p>\n (b) (i) When NaCl is added to AgNO3<\/sub>, a white precipitate of AgCl is formed due to the combination of Cl–<\/sup> ions from NaCl with Ag+<\/sup> ions from AgNO3<\/sub>. Section – B<\/strong> Question 5. (b) (i) Ionisation isomerism Question 6. (b) Potassium permanganate crystals (KMnO4<\/sub>) from pyrolusite: Question 7. (b) Lanthanide contraction Section – C<\/strong> Question 8. Question 9. (b) Distinction between:
\n(Answer all questions)<\/strong><\/p>\n
\n(a) Fill in the blanks by choosing the appropriate word\/words from those given in the brackets: [5]
\n(Henry\u2019s, aldol condensation, absence, do not, ohm, Raoult\u2019s, increases, common ion effect, easily, three, solubility product, ohm-1<\/sup>, two, four, ohm-1<\/sup>, cm2<\/sup>, Cannizzaro, ohm-1<\/sup> cm-1<\/sup>, zero, decreases, presence)
\n(i) Ideal solutions obey ………. law and they …………. form azeotropic mixtures.
\n(ii) Benzaldehyde undergoes ……….. reaction due to ………… of an \u03b1-hydrogen atom.
\n(iii) The solubility of silver chloride ……… in the presence of sodium chloride because of ……….
\n(iv) The unit of conductance is ………. and that of specific conductance is ………..
\n(v) When the concentration of a reactant of the first-order reaction is doubled, the rate becomes ……… times, but for ……….. order reaction, the rate remains the same.<\/p>\n
\n(i) The electrochemical equivalent is the amount of substance which gets deposited from its solution on passing electrical charge equal to:
\n(1) 96,500 Coulombs
\n(2) 1 Coulomb
\n(3) 60 Coulombs
\n(4) 965 Coulombs<\/p>\n
\n(1) Square planar and diamagnetic
\n(2) Tetrahedral and Paramagnetic
\n(3) Square planar and paramagnetic
\n(4) Tetrahedral and Diamagnetic<\/p>\n
\n(1) Glycine
\n(2) Amino acids
\n(3) Urea
\n(4) Proteins<\/p>\n
\n(1) Red
\n(2) Black
\n(3) Orange
\n(4) Green<\/p>\n
\n(1) CH3<\/sub>CH2<\/sub>Cl
\n(2) ClCH2<\/sub>COOH
\n(3) CH3<\/sub>Cl
\n(4) CH3<\/sub>COCl<\/p>\n
\n(i) What is the order of reaction whose rate constant has the same unit as the rate of reaction?
\n(ii) What is the pH value of a solution whose hydroxyl ion concentration is 1 \u00d7 10-2<\/sup> M?
\n(iii) Calculate the number of coulombs required to deposit 5.4 g of Al when the electrode reaction
\nis: Al3<\/sub> + 3e–<\/sup> + Al [Atomic Weight of Al 27 g\/mol].
\n(iv) Write the reaction to prepare acetaldehyde from hydrogen gas and acid chloride.
\n(v) The edge length of the unit cell of a body-centred cubic (bcc) crystal is 352 pm. Calculate the radius of the atom.<\/p>\n\n\n
\n (i) Weak electrolyte<\/td>\n (a) pH of a solution<\/td>\n<\/tr>\n \n (ii) Colour in crystals<\/td>\n (b) Iodoform<\/td>\n<\/tr>\n \n (iii) Acetone<\/td>\n (c) Tollen\u2019s reagent<\/td>\n<\/tr>\n \n (iv) Sorensen<\/td>\n (d) Ostwald dilution law<\/td>\n<\/tr>\n \n (v) Ammoniacal silver nitrate<\/td>\n (e) F – centre<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\n(a) (i) Raoult\u2019s, do not
\n(ii) Cannizzaro, absence
\n(iii) decreases, common ion effect
\n(iv) ohm-1<\/sup>, ohm-1<\/sup>, cm-1<\/sup>
\n(v) two, zero<\/p>\n
\n(ii) -1
\n(iii) -3
\n(iv) -4
\n(v) -2
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-1.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-2.png\")
\n(d) (i) (d)
\n(ii) (e)
\n(iii) (b)
\n(iv) (a)
\n(v) (c)<\/p>\n
\n(Answer any two questions)<\/strong><\/p>\n
\n(a) (i) A10% aqueous solution of cane sugar (mol. wt. 342) is isotonic with 1.754% aqueous solution of urea. Find the molecular mass of urea. [2]
\n(ii) The molecular weight of an organic compound is 58 g mol-1<\/sup>. What will be the boiling point of a solution containing 48 grams of the solute in 1200 grams of water? [2]
\n[Kb<\/sub> for water = 0.513\u00b0C kg mole-1<\/sup>; Boiling point of water = 100\u00b0C]
\n(iii) What will be the value of Van\u2019t Hoff factor (i) of benzoic acid if it dimerises in aqueous solution? How will the experimental molecular weight vary as compared to the normal molecular weight? [1]
\n(b) (i) Determine thepHvalueof 0.001 M acetic acid solution if it is 2% ionised at this concentration. How can the degree of dissociation of this acetic acid solution be increased? [2]
\n(ii) The solubility product of PbCl2<\/sub> at 298K is 1.7 \u00d7 10-5<\/sup>. Calculate the solubility of PbCl2<\/sub> in g\/lit. at 298K. [2]
\nAtomic Weights: [Pb = 207 and Cl = 35.5]
\n(c) Graphite is anisotropic with respect to the conduction of electric current. Explain. [1]
\nAnswer:
\n(a) (i) 10% aqueous solution of cane sugar is isotonic with 1.754% aqueous solution of urea (MB<\/sub>)
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-3.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-4.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-5.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-6.png\")
\n(c) This is due to its chemical bonding properties. In graphite, there are C-atoms arranged in hexagonal layers which are held together by weak van der Waals forces of attraction.<\/p>\n
\n(a) (i) In a body centred and face centred arrangement of atoms of an element, what will be the number of atoms present in respective unit cells? Justify your answer with a calculation. [2]
\n(ii) A compound AB has a simple cubic structure and has molecular mass 99. Its density is 3.4 g cm-3<\/sup>. What will be the edge length of the unit cell? [2]
\n(b) (i) For the reaction:
\n\\(\\begin{array}{c}{2 \\mathrm{NO}_{(\\mathrm{g})} \\rightleftharpoons \\mathrm{N}_{2(\\mathrm{g})}+\\mathrm{O}_{2(\\mathrm{g})} ; \\Delta \\mathrm{H}=-\\text { heat }} \\\\ {\\mathrm{K}_{\\mathrm{e}}=2.5 \\times 10^{2} \\mathrm{at} 298 \\mathrm{K}}\\end{array}\\)
\nwhat will happen to the concentration of N2<\/sub> if:
\n(1) Temperature is decreased to 273 K.
\n(2) The pressure is reduced
\n(ii) In a first-order reaction, 10% of the reactant is consumed in 25 minutes. Calculate: [2]
\n(1) The half-life period of the reaction.
\n(2) The time required for completing 87.5% of the reaction.
\n(c) Water acts as Bronsted acid as well as a Bronsted base. Give one example each to illustrate this statement. [2]
\nAnswer.
\n(a) (i) In bed unit cell, the atoms are present only at the comers of a cube.
\nTotal number of atoms in one unit cell = \\(8 \\times \\frac{1}{8}\\) = 1
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-7.png\")
\nIn face centred cubic unit cell,
\nThe atoms are present at the comers as well as at the centres of six faces of a cube.
\nTotal number of atoms in one unit cell
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-8.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-9.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-10.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-11.png\")
<\/p>\n
\n(a) (i) Consider the following cell reaction at 298 K: [3]
\n2Ag+<\/sup> + Cd \u2192 2Ag + Cd2+<\/sup>
\nThe standard reduction potentials (E\u00b0) for Ag+<\/sup>\/Ag and Cd2-<\/sup>\/Cd are 0.80 V and -0.40 V respectively:
\n(1) Write the cell representation.
\n(2) What will be the emf of the cell if the concentration of Cd2+<\/sup> is 0.1M and that of Ag+<\/sup> is 0.2 M?
\n(3) Will the cell work spontaneously for the condition given in (2) above?
\n(ii) What is a buffer solution? How is it prepared? Explain the buffer action of a basic buffer with a suitable example. [2]
\n(b) Explain the following: [2]
\n(i) When NaCl is added to AgNO3<\/sub> solution, a white precipitate is formed.
\n(ii) An aqueous solution of ammonium chloride is acidic in nature.
\n(c) A 0.05 M NH4<\/sub>OH solution offers the resistance of 50 ohms to a conductivity cell at 298 K. If the cell constant is 0.50 cm-1<\/sup> and molar conductance of NH4<\/sub>OH at infinite dilution is 471.4 ohm-1<\/sup> cm2<\/sup> mol-1<\/sup>, calculate:
\n(i) Specific conductance
\n(ii) Molar conductance
\n(iii) Degree of dissociation
\nAnswer:
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-12.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-13.png\")
\n(3) Since Ecell<\/sub> is +ve, the cell will work spontaneously.
\n(ii) Buffer solution: It is a solution whose pH remains unchanged on the addition of a small amount of acid or base or on dilution.
\nPreparation of buffer solution: A buffer solution can be prepared by mixing weak acid and its salt with a strong base or a weak base and its salt with the strong acid.
\nThe action of a basic buffer
\nLet us consider a basic buffer obtained by mixing solutions containing 1 mole of NH4<\/sub>OH and 1 mole of NH4<\/sub>Cl. Its pH value is nearly 9.25.
\nIn the solution there will be a large concentration of \\(\\mathrm{NH}_{4}^{+}\\) and Cl–<\/sup> ions and unionised NH4<\/sub>OH molecules.<\/p>\n
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-14.png\")
\nAccording to Le-Chatelier\u2019s principle, due to the removal of OH ions, the equilibrium (1) will shift towards r.h.s., giving more of OH–<\/sup> ions and original concentration of OH–<\/sup> ions is restored. Therefore, pH of the solution remains unchanged.<\/p>\n
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-15.png\")
<\/p>\n
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-16.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-17.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-18.png\")
<\/p>\n
\n(Answer any two questions)<\/strong><\/p>\n
\n(a) Write the IUPAC names of the following: [2]
\n(i) [CO(NH3<\/sub>)4<\/sub>SO4<\/sub>]NO3<\/sub>
\n(ii) K[Pt(NH3<\/sub>)Cl3<\/sub>]
\n(b) What type of isomerism is exhibited by the following pairs of compounds: [1]
\n(i) [PtCl2<\/sub>(NH3<\/sub>)4<\/sub>]Br2<\/sub> and [PtBr2<\/sub>(NH3<\/sub>)4<\/sub>]Cl2<\/sub>
\n(ii) [Cr(SCN)(H2<\/sub>O)5<\/sub>]2+<\/sup> and [Cr(NCS)(H2<\/sub>O)5<\/sub>]2+<\/sup>
\n(c) How does K2<\/sub>[PtCl4<\/sub>] get ionised when dissolved in water? Will it form a precipitate when AgNO3<\/sub> solution is added to it? Give a reason for your answer. [2]
\nAnswer.
\n(a) [CO(NH3<\/sub>)5<\/sub> SO4<\/sub>] NO3<\/sub>
\npenta ammine sulphato cobalt (III) nitrate
\nK [Pt (NH3<\/sub>) Cl3<\/sub>]
\npotassium ammine tri chlorido platinate (II)<\/p>\n
\n(ii) Linkage isomerism
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-19.png\")
\nIt gives no chloride ion in solution, therefore, it will not form a precipitate with AgNO3<\/sub> solution.<\/p>\n
\n(a) Give balanced equations for the following reactions: [3]
\n(i) Silver nitrate is added to the dilute solution of sodium thiosulphate.
\n(ii) Potassium dichromate is treated with acidified ferrous sulphate solution.
\n(iii) Phosphorus reacts with cone, sulphuric acid.
\n(b) How will you obtain pure potassium permanganate (KMnO4<\/sub>) crystals from its ore, pyrolusite? Give the steps involved and the reactions. [2]
\nAnswer:
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-20.png\")
<\/p>\n
\nIt involves two steps
\nStep-1: Conversion of pyrolusite into potassium manganate
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-21.png\")
\nStep-2: Conversion of potassium manganate into potassium permanganate (By isolation)
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-22.png\")
\nOn crystallisation, the crystals of KMnO4<\/sub> appear, which are separated and dried.<\/p>\n
\n(a) (i) Sulphur dioxide acts as an oxidizing agent as well as a reducing agent. Give one reaction each to show its oxidizing nature and its reducing nature. [3]
\n(ii) Explain why an aqueous solution of potassium hexacyanoferrate (II) does not give the test for ferrous ion. [2]
\n(b) What is meant by Lanthanide contraction? Write the general electronic configuration of inner transition elements. [2]
\nAnswer:
\n(a) (i) 1. SO2<\/sub> as an oxidising agent
\n2Mg + SO2<\/sub> \u2192 2MgO + S
\n(Burning)
\n2. SO2<\/sub> as a reducing agent
\nSO2<\/sub> + Br2<\/sub> + 2H2<\/sub>O \u2192 H2<\/sub>SO4<\/sub> + 2HBr
\n(ii) Potassium hexacyanoferrate (II) does not give ferrous (Fe2+<\/sup>) ions in solution because it is complex and Fe2+<\/sup> ions are in the coordination sphere and form coordinate bonds with cyanide, CN–<\/sup> ligands.<\/p>\n
\nIt is the slow or gradual decrease in the sizes of atoms or tri positive ions of lanthanide as we move from left to right along the lanthanides.
\nGeneral electronic configuration of inner transition elements is
\n[Xe]54<\/sub> 4f1-14<\/sup> 5d0-1<\/sup> 6s2<\/sup> – For lanthanides
\n[Rn]86<\/sub> 5f1-14<\/sup> 6d0-1<\/sup> 7s2<\/sup> – For actinides<\/p>\n
\n(Answer any two questions)<\/strong><\/p>\n
\n(a) How can the following conversions be brought about:
\n(i) Acetaldehyde to acetaldehyde phenyl hydrazone. [1]
\n(ii) Benzoic acid to aniline. [1]
\n(iii) Methyl chloride to acetone. [2]
\n(iv) Benzene to benzene diazonium chloride. [1]
\n(b) (i) Glycerol (propane 1, 2, 3 triol) is more viscous than ethylene glycol (ethane 1, 2, diol). Explain [1]
\n(ii) How can urea be detected by Biuret test? [1]
\n(c) Identify the compounds A, B and C: [3]
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-23.png\")
\nAnswer:
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-24.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-25.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-26.png\")
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-27.png\")
<\/p>\n
\n(a) Give balanced equations for the following name reactions:
\n(i) Benzoin condensation
\n(ii) Wurtz-Fitting reaction
\n(iii) Carbylamine reaction
\n(b) Give the chemical test to distinguish:
\n(i) Formaldehyde and acetaldehyde
\n(ii) Dimethyl ether and ethyl alcohol.
\n(c) (i) Write the structure of three ethers with molecular formula C4<\/sub>H10<\/sub>O.
\n(ii) Starting with Grignard\u2019s reagent, how will you prepare propanoic acid?
\nAnswer:
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-28.png\")
<\/p>\n
\n(i) Formaldehyde and acetaldehyde
\nAcetaldehyde, when heated with I2<\/sub> and NaOH, gives a yellow precipitate of iodoform (Iodoform test) whereas formaldehyde does not give a yellow precipitate of iodoform.
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-29.png\")
\n(ii) Dimethyl ether and ethyl alcohol: C2<\/sub>H5<\/sub>OH, when heated with I2<\/sub>and NaOH, gives yellow precipitate crystals of iodoform (Iodoform test) whereas diethyl ether does not give a yellow precipitate with I2<\/sub> and NaOH.
\n![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-30.png\")
<\/p>\n
![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-31.png\")
![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-32.png\")
![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-33.png\")
![\"ISC](\"https:\/\/www.aplustopper.com\/wp-content\/uploads\/2020\/12\/ISC-Chemistry-Question-Paper-2016-Solved-for-Class-12-image-34.png\")
<\/p>\n