{"id":4442,"date":"2019-12-17T12:53:18","date_gmt":"2019-12-17T07:23:18","guid":{"rendered":"https:\/\/versionweekly.com\/?p=4442"},"modified":"2019-12-17T12:59:59","modified_gmt":"2019-12-17T07:29:59","slug":"cbse-sample-question-papers-for-class-12-chemistry-2020-board-exam-pdf-download","status":"publish","type":"post","link":"https:\/\/versionweekly.com\/news\/cbse\/cbse-sample-question-papers-for-class-12-chemistry-2020-board-exam-pdf-download\/","title":{"rendered":"CBSE Sample Question Papers for Class 12 Chemistry 2020 Board Exam PDF Download"},"content":{"rendered":"
SAMPLE PAPER XII 2019-20
\nCHEMISTRY<\/p>\n
Time : 3 hrs.\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0M. Marks : 70<\/p>\n
General Instructions<\/p>\n
SECTION – A<\/strong><\/p>\n Read the given passage and answer the Questions 1 to 5 that follow:<\/p>\n A Lead storage battery is the most important type of secondary cell having a lead anode and a grid of lead packed with PbO2<\/sub> as cathode. A 38% solution of sulphuric acid is used as electrolyte. (Density=1.294 g mL-1<\/sup>) The battery holds 3.5 L of the acid. During the discharge of the battery, the density of H2<\/sub>SO4<\/sub> falls to 1.139 g mL-1<\/sup>. (20% H2<\/sub>SO4 <\/sub>by mass)<\/p>\n Question 1. Question 2. Question 3. Question 4. Question 5. Questions 6 to 10 are one word answers:<\/p>\n Question 6. Question 7. Question 8. Question 9. Question 10. Questions 11 to 1 5 are multiple choice questions:<\/p>\n Question 11. Question 12. Question 13. Question 14. Question 15. Questions 16 to 20:<\/p>\n (A) Both assertion and reason are correct statements, and reason is the correct explanation of the assertion. Question 16. Question 17. Question 18. Question 19. Question 20. SECTION: B<\/strong><\/p>\n Question 21. Question 22. Question 23. Question 24. Question 25. Question 26. Question 27. SECTION: C<\/strong><\/p>\n Question 28. Question 29. Question 30. Question 31. Question 32. Question 33. (b) Arrange the following compounds in increasing order of their acid strength: Question 34. SECTION: D<\/strong><\/p>\n Question 35. (b) Aqueous solution of copper sulphate and silver nitrate are electrolysed by 1 ampere current for 10 minutes in separate electrolytic cells. Will the mass of copper and silver deposited on the cathode be same or different? Explain your answer.<\/p>\n OR<\/p>\n (a) Calculate the degree of dissociation of 0.0024 M acetic acid if conductivity of this solution is 8.0 \u00d7 10-5<\/sup> S cm-1<\/sup>. Question 36. OR<\/p>\n (a) How will you convert: (b) Write the structures of A and B in the following: Question 37. (b) Describe the cause of the following variations with respect to lanthanoids and actinoids: OR<\/p>\n (a) What happens when (b) Explain the following trends in the properties of the members of the First series of transition elements: CBSE Class 12 Sample Papers are provided hereby Versionweekly for students to make them prepare for their final board exams. These sample papers are designed by our subject experts and as per the latest syllabus(2019-20). All the sample papers are prepared in PDF format, so that students can easily download them and practice offline as well. These sample papers are available here for Physics, Chemistry, Maths and Biology subjects.<\/p>\n
\nWrite the reaction taking place at the cathode when the battery is in use.<\/p>\n
\nHow much electricity in terms of Faraday is required to carry out the reduction of one mole of PbO2<\/sub>?<\/p>\n
\nWhat is the molarity of sulphuric acid before discharge?<\/p>\n
\nLead storage battery is considered a secondary cell. Why?<\/p>\n
\nWrite the products of electrolysis when dilute sulphuric acid is electrolysed using Platinum electrodes.<\/p>\n
\nName the substance used as depressant in the separation of two sulphide ores in Froth floatation method.<\/p>\n
\nName the unit formed by the attachment of a base to 1′ position of sugar in a nucleoside.<\/p>\n
\nName the species formed when an aqueous solution of amino acid is dissolved in water?<\/p>\n
\nWhat type of reaction occurs in the formation of Nylon 6,6 polymer?<\/p>\n
\nWhich of the following compounds would undergo cannizzaro reaction:
\nBenzaldehyde, Cyclohexanone, 2- Methylpentanal.<\/p>\n
\nThe IUPAC name of the compound shown below is:
\n
\n(a) 2-bromo-6-chlorocyclohex-1 -ene
\n(b) 6-bromo-2-chlorocyclohexene
\n(c) 3-bromo-1 -chlorocyclohexene
\n(d) 1 -bromo-3 -chlorocyclohexene<\/p>\n
\nWhen one mole of CoCl3<\/sub>.5NH3<\/sub> was treated with excess of silver nitrate solution, 2 mol of AgCl was precipitated. The formula of the compound is:
\n(a) [Co(NH3<\/sub>)5<\/sub>Cl2<\/sub>]Cl
\n(b) [Co(NH3<\/sub>)5<\/sub>Cl]Cl2<\/sub>
\n(c) [Co(NH3<\/sub>)4<\/sub>Cl2<\/sub>] (NH3<\/sub>)Cl
\n(d) [Co(NH3<\/sub>)3<\/sub>Cl3<\/sub>] (NH3<\/sub>)2<\/sub><\/p>\n
\nThe absorption maxima of several octahedral complex ions are as follows:
\n
\nThe crystal field splitting is maximum for :
\n(a) [Co(H2<\/sub>O)6<\/sub>]3+<\/sup>
\n(b) [Co(CN)6<\/sub>]3-<\/sup>
\n(c) [Co(NH3<\/sub>)6<\/sub>]3+<\/sup>
\n(d) All the complex ions have the same splitting, \u03940<\/sub>,<\/p>\n
\nPredict the number of ions produced per formula unit in an aqueous solution of [Co(en)3<\/sub>]Cl3<\/sub>
\n(a) 4
\n(b) 3
\n(c) 6
\n(d) 2<\/p>\n
\nThe incorrect statement about LDP is:
\n(a) It is obtained through the free radical addition of ethene.
\n(b) It consists of linear molecules.
\n(c) It is obtained by the H-atom abstraction.
\n(d) Peroxide is used as an initiator.<\/p>\n
\n(B) Both assertion and reason are correct statements, but reason is not the correct explanation of the assertion.
\n(C) Assertion is correct, but reason is wrong statement.
\n(D) Assertion is wrong, but reason is correct statement.<\/p>\n
\nAssertion: The two strands in double strand helix structure of DNA are complementary to each other
\nReason: Disulphide bonds are formed between specific pairs of bases<\/p>\n
\nAssertion: Glucose reacts with hydroxylamine to form an oxime and also adds a molecule of hydrogen cyanide to give cyanohydrin.
\nReason: The carbonyl group is present in the open chain structure of glucose.<\/p>\n
\nAssertion: The acidic strength of halogen acids varies in the order
\nHF>HCl>HBr>HI
\nReason: The bond dissociation enthalpy of halogen acids decreases in the order HF>HCl>HBr>HI<\/p>\n
\nAssertion: C2<\/sub>H5<\/sub>OH is a weaker base than phenol but is a stronger nucleophile than phenol.
\nReason: In phenol the lone pair of electrons on oxygen is withdrawn towards the ring due to resonance.<\/p>\n
\nAssertion: Aryl halides undergo nucleophilic substitution reactions with ease.
\nReason: The carbon halogen bond in aryl halides has partial double bonds character.<\/p>\n
\nCalculate the number of lone pairs on central atom in the following molecule and predict the geometry. XeF4<\/sub><\/p>\n
\nThe rate of a reaction depends upon the temperature and is quantitatively expressed as
\n
\n(i) If a graph is plotted between log k and 1\/T, write the expression for the slope of the reaction?
\n(ii) If at under different conditions Ea1<\/sub> and Ea2<\/sub> are the activation energy of two reactions If E a1<\/sub> = 40 J\/mol and E a2<\/sub> = 80 J\/mol. Which of the two has a larger value of the rate constant?<\/p>\n
\nThe experimentally determined molar mass for what type of substances is always lower than the true value when water is used as solvent. Explain. Give one example of such a substance and one example of a substance which does not show a large variation from the true value.<\/p>\n
\nWrite structure of the products formed:
\n<\/p>\n
\nDraw one of geometrical isomers of the complex [ Pt(en)2<\/sub>Cl2<\/sub>]2+<\/sup> which is optically inactive. Also write the name of this entity according to the IUPAC nomenclature.
\nOR
\nDiscuss the bonding in the coordination entity [CO( NH3<\/sub>)6<\/sub>]3+<\/sup> on the basis of valence bond theory. Also, comment on the geometry and spin of the given entity. (Atomic no. of Co = 27)<\/p>\n
\nWhat is meant by Vapour phase refining? Write any one example of the process which illustrates this technique, giving the chemical equations involved.
\nOR
\nWrite and explain the reactions involved in the extraction of gold.<\/p>\n
\nWhich one of the following compounds will undergo hydrolysis at a faster rate by SN<\/sub>1 mechanism? Justify.
\n<\/p>\n
\nCalculate the freezing point of a solution containing 0.5g KCl (Molar mass = 74.5 g\/mol) dissolved in 100 g water, assuming KCl to be 92% ionized. Kf<\/sub>of water = 1.86 K kg \/ mol.<\/p>\n
\nFor the reaction A + B \u2192 products, the following initial rates were obtained at various given initial concentrations
\n
\nDetermine the half-life period.
\nOR
\nA first order reaction is 50 % complete in 50 minutes at 300 K and the same reaction is again 50 % complete in 25 minutes at 350 K. Calculate activation energy of the reaction.<\/p>\n
\nAnswer the following questions:
\n(a) Which of the following electrolytes is most effective for the coagulation of AgI\/Ag+<\/sup> sol?
\nMgCl2<\/sub>, K2<\/sub>SO4<\/sub>, K4<\/sub>[Fe(CN)6<\/sub>]
\n(b) What happens when a freshly precipitated Fe(OH)3<\/sub> is shaken with a little amount of dilute solution of FeCl3<\/sub>.
\n(c) Out of sulphur sol and proteins, which one forms macromolecular colloids?<\/p>\n
\nAccount for the following:
\na) Moist SO2<\/sub> decolourises KMnO4<\/sub> solution.
\nb) In general interhalogen compounds are more reactive than halogens (except fluorine).
\nc) Ozone acts as a powerful oxidizing agent<\/p>\n
\nIdentify the product formed when propan -1- ol is treated with Conc. H2<\/sub>SO4<\/sub> at 413 K. Write the mechanism involved for the above reaction.<\/p>\n
\n(a) Give chemical tests to distinguish between the following pairs of compounds:
\n(i) Ethanal and Propanone.
\n(ii) Pentan-2-one and Pentan-3-one.<\/p>\n
\nBenzoic acid, 4- Nitrobenzoic acid, 3,4-Dinitrobenzoic acid, 4- Methoxybenzoic acid.
\nOR
\nCompare the reactivity of benzaldehyde and ethanal towards nucleophilic addition reactions. Write the cross aldol condensation product between benzaldehyde and ethanal.<\/p>\n
\nDefine and write an example for the following :
\n(a) Broad spectrum antibiotics.
\n(b) Analgesics<\/p>\n
\n(a) The e.m.f. of the following cell at 298 K is 0.1745V
\n
\nCalculate the H+<\/sup> ions concentration of the solution at the electrode where hydrogen is being produced.<\/p>\n
\n
\n(b) Solutions of two electrolytes \u2018A\u2019 and \u2018B\u2019 are diluted. The limiting molar conductivity of \u2018B\u2019 increases to a smaller extent while that of \u2018A\u2019 increases to a much larger extent comparatively. Which of the two is a strong electrolyte? Justify your answer.<\/p>\n
\nAn organic compound A\u2019 with molecular formula C7<\/sub>H7<\/sub>NO reacts with Br2<\/sub>\/aqKOH to give compound B\u2019, which upon reaction with NaNO2<\/sub> & HCl at O\u00b0C gives C\u2019. Compound C\u2019 on heating with CH3<\/sub>CH2<\/sub>OH gives a hydrocarbon D\u2019. Compound B\u2019 on further reaction with Br2<\/sub> water gives white precipitate of compound E\u2019. Identify the compound A, B, C, D & E; also justify your answer by giving relevant chemical equations.<\/p>\n
\n(i) Aniline into Fluorobenzene.
\n(ii) Benzamide into Benzylamine.
\n(iii) Ethanamine to N,N-Diethylethanamine.<\/p>\n
\n<\/p>\n
\n(a) When a chromite ore (A) is fused with an aqueous solution of sodium carbonate in free excess of air, a yellow solution of compound (B) is obtained. This solution is filtered and acidified with sulphuric acid to form compound (C). Compound (C) on treatment with solution of KCl gives orange crystals of compound (D). Write the chemical formulae of compounds A to D.<\/p>\n
\n(i) Greater range of oxidation states of actinoids as compared to lanthanoids.
\n(ii) Greater actinoid contraction as compared to lanthanoid contraction.
\n(iii) Lower ionisation enthalpy of early actinoids as compared to the early lanthanoids.<\/p>\n
\n(i) Manganate ions (MnO2-<\/sup>4<\/sub>) undergoes disproportionation reaction in acidic medium?
\n(ii) Lanthanum is heated with Sulphur?<\/p>\n
\n(i) Eo<\/sup> (M2+<\/sup> \/ M) value for copper is positive(+0.34 V) in contrast to the other members of the series.
\n(ii) Cr2+<\/sup> is reducing while Mn3+<\/sup> is oxidising, though both have d4<\/sup> configuration.
\n(iii) The Oxidising power in the series increases in the order VO+<\/sup>2<\/sub> < Cr2<\/sub>O2-<\/sup>7<\/sub> < MnO–<\/sup>4<\/sub><\/p>\nCBSE Sample Papers for Class 12 with Marking Scheme and Solutions PDF Download for 2020 Exams<\/h2>\n