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ISC Class XII Board Specimen 2022 : Chemistry [Semester 2]

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ISC 12th
Indian School Certificate Examination (ISC), New Delhi

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ISC SEMESTER 2 EXAMINATION SPECIMEN QUESTION PAPER CHEMISTRY PAPER 1 (THEORY) ---------------------------------------------------------------------------------------------------Maximum Marks: 35 Time allowed: One and a half hour Candidates are allowed an additional 10 minutes for only reading the paper. They must NOT start writing during this time. --------------------------------------------------------------------------------------------------------------------- All questions are compulsory The intended marks for questions or parts of questions are given in brackets. [ ] All working, including rough work, should be done on the same sheet as, and adjacent to the rest of the answer. Balanced equations must be given wherever possible and diagrams where they are helpful. When solving numerical problems, all essential working must be shown. In working out problems, use the following data: Gas constant R = 1 987 cal deg-1 mol-1 = 8 314 JK-1 mol-1 = 0 0821 dm3 atm K-1mol-1 1 l atm = 1 dm3 atm = 101 3 J. 1 Faraday = 96500 coulombs. Avogadro s number = 6 023 1023. --------------------------------------------------------------------------------------------------------------------- SECTION A 7 MARKS Question 1 Fill in the blanks by choosing the appropriate word(s) from those given in the brackets: (two, four, sec-1, diamagnetic, acetaldehyde, mol-1L sec-1, paramagnetic, formaldehyde, acetone, ethanol) (i) When the concentration of a reactant of first order reaction is doubled, the rate of reaction becomes ___________ times. The unit of rate constant (k) for the first order reaction is __________. [1] (ii) The transition metals show ___________ character because of the presence of unpaired electrons while Cu+ is ___________ because its electronic configuration is [Ar]3d10. [1] (iii) Calcium formate on distillation gives ___________ but the distillation of calcium formate and calcium acetate gives ___________. [1] 1 Question 2 Select and write the correct alternative from the choices given below. (i) (ii) (iii) (iv) The type of hybridization involved in Octahedral complexes is: (a) sp3 (b) dsp2 (c) sp3d (d) d2sp3 One mole of a symmetrical alkene on ozonolysis gives two moles of an aldehyde having a molecular mass of 44 amu. The alkene is: (a) ethene (b) propene (c) 1-butene (d) 2-butene Primary amine when warmed with chloroform and alc. KOH yields: (a) cyanides (b) isocyanides (c) benzene diazonium chloride (d) secondary amines Assertion: The conversion of fresh precipitate to colloidal state is called peptization. Reason: It is caused by addition of common ions. (a) Both assertion and reason are true and reason is the correct explanation of assertion. (b) Both assertion and reason are true but reason is not the correct explanation for assertion. (c) Assertion is true but reason is false. (d) Assertion is false but reason is true. 2 [1] [1] [1] [1] SECTION B 16 MARKS Question 3 [2] Name the type of isomerism shown by each of the following pairs of compounds: (i) [CoCl2(NH3)4]Cl.H2O and [CoCl(H2O)(NH3)4]Cl2 (ii) [Cr(NH3)5Br]SO4 and [Cr(NH3)5SO4]Br Question 4 (i) [2] Write chemical equations to illustrate each of the following name reactions: (a) Rosenmund s reduction (b) Clemmensen s reduction OR (ii) How will you bring about the following conversions? (Give equation). (a) Acetic acid to acetone (b) Formaldehyde to urotropine Question 5 [2] What is a zwitter ion? Represent the zwitter ion of glycine. Question 6 [2] (i) Arrange the following in the increasing order of their basic strength: C2H5NH2, C6H5NH2, (C2H5)2NH. (ii) What are the products formed when benzene diazonium chloride reacts with phenol in weak alkaline medium? (Give equation). Question 7 [2] Give reasons for the following: (i) Diabetic patients are advised to take artificial sweeteners instead of natural sweeteners. (ii) The use of aspartame is limited to cold foods and drinks. 3 Question 8 [2] The rate of reaction becomes four times when the temperature changes from 293K to 313K. Calculate the energy of activation (Ea) of the reaction assuming that it does not change with temperature. (R = 8 314 JK-1mol-1) Question 9 [2] Give balanced equation for each of the following: (i) Ethylamine and nitrous acid (ii) Aniline and acetyl chloride Question 10 [2] Give one chemical test for each to distinguish between the following pairs of compound: (i) Acetaldehyde and benzaldehyde (ii) Acetone and acetic acid SECTION C 12 MARKS Question 11 (i) [3] Answer the following: (a) Define molecularity of a reaction. Give one difference between the order of reaction and its molecularity. (b) The rate constant (k) of a first order reaction is 4 5 x 10-2 sec-1. What will be the time required for the initial concentration of 0 4 M of the reactant to be reduced to 0 2 M? OR (ii) Answer the following: (a) For a first order reaction, show that the time required for the completion of 99% reaction is twice the time required for the completion of 90% of the reaction. (b) For a reaction, rate = k[A]1[B]1.5[C]0. What is the overall order of reaction? 4 Question 12 [3] (i) What is the basic difference between the electronic configuration of transition and inner transition elements? (ii) Why are Zn2+ ions colourless while Ni2+ ions are green in colour? Question 13 (i) (ii) [3] Write the formula of each of the following compounds: (a) Potassium trioxalatoaluminate (III) (b) Triammine triaquachromium (III) chloride For the complex ion [Co(NH3)6]3+, state the oxidation state of central metal atom and the coordination number of the complex ion. Question 14 [3] Give reason for each of the following: (i) For ferric hydroxide sol. the coagulating power of phosphate ion is more than chloride ion. (ii) Lyophilic colloidal solutions are more stable than lyophobic colloidal solutions. (iii) Gelatin is added to ice cream. 5

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