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Board Paper of Class 12-Science 2016 Chemistry (SET 2) - Solutions

General Instructions :
(i) All questions are compulsory.
(ii) Q. no. 1 to 5 are very short answer questions and carry 1 mark each.
(iii) Q. no. 6 to 10 are short answer questions and carry 2 marks each.
(iv) Q. no. 11 to 22 are also short answer questions and carry 3 marks each.
(v) Q. no. 23 is a value based question and carry 4 marks.
(vi) Q. no. 24 to 26 are long answer questions and carry 5 marks each.
(vii) Use log tables if necessary, use of calculators is not allowed.

  • Question 1
    Write the IUPAC name of the given compound:


  • Question 2
    Write the main reason for the stability of colloidal sols. VIEW SOLUTION

  • Question 3
    Out of  and , which is more reactive towards SN1 reaction and why? VIEW SOLUTION

  • Question 4
    On adding NaOH to ammonium sulphate, a colourless gas with pungent odour is evolved, which forms a blue-coloured complex with Cu2+ ion. Identify the gas. VIEW SOLUTION

  • Question 5
    What type of magnetism is shown by a substance if magnetic moments of domains are arranged in same direction? VIEW SOLUTION

  • Question 6
    For a reaction : 2NH3(g)PtN2(g)+3H2(g)          Rate = k
    (i) Write the order and molecularity of this reaction.

    (ii) Write the unit of k. VIEW SOLUTION

  • Question 7
    Write the mechanism of the following reaction:


  • Question 8
    From the given cells:
    Lead storage cell, Mercury cell, Fuel cell and Dry cell
    Answer the following:
    (i) Which cell is used in hearing aids?
    (ii) Which cell was used in Apollo Space Programme?
    (iii) Which cell is used in automobiles and inverters?
    (iv) Which cell does not have long life? VIEW SOLUTION

  • Question 9
    When chromite ore FeCr2O4 is fused with NaOH in presence of air, a yellow-coloured compound (A) is obtained, which on acidification with dilute sulphuric acid gives a compound (B). Compound (B) on reaction with KCl forms an orange coloured crystalline compound (C).

    (i) Write the formulae of the compounds (A), (B) and C.
    (ii) Write one use of compound (C).


    Complete the following chemical equations:
    (i) 8MnO4-+3S2O32-+H2O 
    (ii) Cr2O72-+3Sn2++14H+  VIEW SOLUTION

  • Question 10
    When a co-ordination compound CrCl3.6H2O is mixed with AgNO3, 2 moles of AgCl are precipitated per mole of the compound. Write
    (i) Structural formula of the complex.
    (ii) IUPAC name of the complex. VIEW SOLUTION

  • Question 11

    (i) Differentiate between adsorption and absorption.

    (ii) Out of MgCl2 and AlCl3, which one is more effective in causing coagulation of negatively charged sol and why?

    (iii) Out of sulphur sol and proteins, which one form multimolecular colloids?


  • Question 12
    (i) Name the method of refining of metals such as Germanium.

    (ii) In the extraction of Al, impure Al2O3 is dissolved in conc. NaOH to form sodium aluminate and leaving impurities behind. What is the name of this process?

    (iii) What is the role of coke in the extraction of iron from its oxides? VIEW SOLUTION

  • Question 13
    Calculate e.m.f of the following cell at 298 K:

    2Cr(s) + 3Fe2+ (0.1M) → 2Cr3+ (0.01M) + 3 Fe(s)

    Given: E°(Cr3+ | Cr) = – 0.74 VE° (Fe2+ | Fe) = – 0.44 V VIEW SOLUTION

  • Question 14
    Given reasons:

    (i) C–Cl bond length in chlorobenzene is shorter than C–Cl bond length in CH3–Cl.

    (ii) The dipole moment of chlorobenzene is lower than that of cyclohexyl chloride.

    (iii) SN1 reactions are accompanied by racemization in optically active alkyl halides. VIEW SOLUTION

  • Question 15
    An element crystallizes in a f.c.c. lattice with cell edge of 250 pm. Calculate the density if 300 g of this element contain 2 × 1024 atoms. VIEW SOLUTION

  • Question 16
    The rate constant for the first-order decomposition of H2O2 is given by the following equation:

    log k=14.2-1.0×104TK

    Calculate Ea for this reaction and rate constant k if its half-life period be 200 minutes.

    (Given: R = 8.314 JK–1 mol–1) VIEW SOLUTION

  • Question 17
    (i) What is the role of t-butyl peroxide in the polymerization of ethene?
    (ii) Identify the monomers in the following polymer:

    (iii) Arrange the following polymers in the increasing order of their intermolecular forces:

        Polystyrene, Terylene, Buna-S

    Write the mechanism of free radical polymerization of ethene. VIEW SOLUTION

  • Question 18
    (i) Write the name of two monosaccharides obtained on hydrolysis of lactose sugar.

    (ii) Why Vitamin C cannot be stored in our body ?

    (iii) What is the difference between a nucleoside and nucleotide ? VIEW SOLUTION

  • Question 19
    (a) For the complex [Fe(CN)6]3–, write the hybridization type, magnetic character and spin nature of the complex. (At. number : Fe = 26).

    (b) Draw one of the geometrical isomers of the complex [Pt(en)2Cl2]2+ which is optically active. VIEW SOLUTION

  • Question 20
    Give reasons:

    (i) Mn shows the highest oxidation state of +7 with oxygen but with fluorine, it shows the highest oxidation state of +4.

    (ii) Transition metals show variable oxidation states.

    (iii) Actinoids show irregularities in their electronic configurations. VIEW SOLUTION

  • Question 21
    Write the main product(s) in each of the following reactions:




  • Question 22
    Write the structures of A, B and C in the following:



  • Question 23

    Due to hectic and busy schedule, Mr. Angad made his life full of tensions and anxiety. He started taking sleeping pills to overcome the depression without consulting the doctor. Mr. Deepak, a close friend of Mr. Angad, advised him to stop taking sleeping pills and suggested to change his lifestyle by doing Yoga, mediation and some physical exercise. Mr. Angad followed his friend's advice and after few days he started feeling better.

    After reading the above passage, answer the following:
    (i) What are the values (at least two) displayed by Mr. Deepak?
    (ii) Why is it not advisable to take sleeping pills without consulting doctor?
    (iii) What are tranquilizers? Give two examples.


  • Question 24

    (a) Calculate the freezing point of solution when 1.9 g of MgCl2 (M = 95 g mol−1) was dissolved in 50 g of water, assuming MgCl2 undergoes complete ionization.
    (Kf for water = 1.86 K kg mol−1)

    (b) (i) Out of 1 M glucose and 2 M glucose, which one has a higher boiling point and why?

    (ii) What happens when the external pressure applied becomes more than the osmotic pressure of solution?


    (a) When 2.56 g of sulphur was dissolved in 100 g of CS2, the freezing point lowered by 0.383 K. Calculate the formula of sulphur (Sx).

    (Kf for CS2 = 3.83 K kg mol−1, Atomic mass of sulphur = 32 g mol−1]

    (b) Blood cells are isotonic with 0.9% sodium chloride solution. What happens if we place blood cells in a solution containing

    (i) 1.2% sodium chloride solution?
    (ii) 0.4% sodium chloride solution?


  • Question 25
    (a) Account for the following :
    (i) Ozone is thermodynamically unstable.
    (ii) Solid PCl5 is ionic in nature.
    (iii) Fluorine forms only one oxoacid HOF.

    (b) Draw the structure of
    (i) BrF5
    (ii) XeF4


    (i) Compare the oxidizing action of F2 and Cl2 by considering parameters such as bond dissociation enthalpy, electron gain enthalpy and hydration enthalpy.

    (ii) Write the conditions to maximize the yield of H2SO4 by contact process.

    (iii) Arrange the following in the increasing order of property mentioned :
    (a) H3PO3, H3PO4, H3PO2 (Reducing character)
    (b) NH3, PH3, AsH3, SbH3, BiH3 (Base strength)

  • Question 26
    Write the structures of A, B, C, D and E in the following reactions:


    (a) Write the chemical equation for the reaction involved in Cannizzaro reaction.
    (b) Draw the structure of the semicarbazone of ethanal.
    (c) Why pKa of F-CH2-COOH is lower than that of Cl−CH2−COOH?
    (d) Write the product in the following reaction:

    (e) How can you distinguish between propanal and propanone? VIEW SOLUTION
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