Orgnisation : Council For Indian School Certificate Examinations
Exam : ISC (Class XII) Chemistry
Document type : Question Paper
Website : cisce.org
Download Sample/Model Question Papers :
https://www.pdfquestion.in/uploads/cisce.org/5922-Chemistry-Paper-1.pdf
Chemistry Question Paper :
Chemistry PAPER – 1
(THEORY) (Three Hours)
PART I (20 Marks)
Related / Similar Question Paper :
cisce.org ISC Chemistry Practical Paper
Answer all questions.(a) Fill in the blanks by choosing the appropriate word/words from those given in the brackets :
(hydrolysis, reduction, oxidation, vacant, osmotic, above, benzoic acid, phenol, aniline, below, can, decreases, increases, cannot, crystal, ionization, rate, rate constant.) [5]
(i) A catalyst ______ start a reaction but it can increase the ______ of the reaction.
(ii) Electrons trapped in the ______ sites of the __________ lattice are called F-centres.
(iii) An aqueous solution of sugar boils ________ 100oC and freezes _______ 0oC.
(iv) Toluene on ________ with alkaline potassium permanganate gives________.
(v) The degree of _________ of ammonium hydroxide ________ on addition of ammonium chloride.
(b) Complete the following statements by selecting the correct alternative from the choices given : [5]
(i) For reaction 2N2O5 -> 2 NO2 + O2, the rate and rate constants are 1.02 x10-4 mole litre-1 sec-1 and 3.4 x 10-5 sec-1 respectively. The concentration of N2O5 at that time will be
(1) 1.732 mol lit-1
(2) 3 mol lit-1
(3) 1.02×10-4 mol lit-1
(4) 3.2×105 mol lit-1
(ii) Ethanoic acid dimerises in solution. Its molecular mass determined from its depression of freezing point of the solution will be
(1) Same as the theoretical value
(2) Half its theoretical value
(3) Double its theoretical value
(4) One third of its theoretical value.
(iii) Magnesium displaces hydrogen from dilute acid solution because
(1) The oxidation potential of magnesium is less than that of hydrogen.
(2) The reduction potential of magnesium is less than that of hydrogen.
(3) Both magnesium and hydrogen have same oxidation potential.
(4) Both magnesium and hydrogen have same reduction potential.
(iv) In the series of reactions
(1) Acetyl chloride
(2) Ammonium acetate
(3) Acetic anhydride
(4) Methyl cyanide.
(v) In the reaction PCl3(g) + Cl2(g) -> PCl5(g), the equilibrium will shift in the opposite direction, if:
(1) Chlorine is added.
(2) PCl3 is added
(3) Pressure is increased
(4) Pressure is reduced.
(c) Answer the following questions : [5]
(i) Among equimolal aqueous solutions of MgCl2, NaCl, FeCl3 and C12H22O11, which will show minimum osmotic pressure? Why?
(ii) The pH of acetic acid decreases on dilution. State the Law governing this statement.
(iii) Xenon gives a series of fluorides, but Helium and Neon do not. Why? (At. No: Xe = 54, Ne = 10, He = 2)
(iv) Calculate the number of coulombs required to deposit 20.25 g of aluminium (at. mass = 27) from a solution containing Al+3.
(d) Match the following : [5]
(i) CHCl3 + NaOH (a) Fluorine
(ii) Proteins (b) Starch
(iii) Carbohydrate (c) Ammonia
(iv) Lewis base (d) Peptide linkage
(v) KHF2 (e) Isocyanide test
Part II : (50 Marks)
Answer six questions choosing two from Section A, two from Section B and two from Section C.
Section A :
Answer any two questions.
Question 2 :
(a) (i) A certain aqueous solution boils at 100.303oC. What is its freezing point? Kb for water = 0.5 K mol-1 and Kf = 1.87 K mol-1. [2]
(ii) A solution containing 1g of sodium chloride in 100g of water freezes at -0.604oC. Calculate the degree of dissociation of sodium chloride. (Na = 23, Cl = 35.5, Kf for water = 1.87 k mol-1) [4]
(b) (i) Explain graphically how the rate of a reaction changes with every 10oC rise in temperature. [2]
(ii) Give one example of zero order reaction. [1]
(iii) The half life period for the decomposition of a substance is 2.5 hours. If the initial weight of the substance is 160 g, how much of the substance will be left after 10 hours? [1]
Question 3 :
(a) (i) Define Frenkel defects of an ionic crystal. [1]
(ii) Iron has an edge length 288 pm. Its density is 7.86 gm/cm-3. Find the type of cubic lattice to which the crystal belongs. (at. mass of iron = 56) [3]
(b) Explain giving reasons why :
(i) Mg(OH)2 is sparingly soluble in water but highly soluble in ammonium chloride solution. [2]
(ii) When H2S is passed through acidified zinc sulphate solution, white precipitate of zinc sulphide is not formed. [2]
(c) The equilibrium constant for the reaction H2(g)+I2(g)-> 2HI(g) is 49.5 at 440oC. If 0.2 mole of H2 and 0.2 mole of I2 are allowed to react in a 10 litre flask at this temperature, calculate the concentration of each at equilibrium. [2]
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