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Board Paper of Class 12-Science 2014 Chemistry (SET 1) - Solutions

General Instructions:
(i) All questions are compulsory
(ii) Question numbers 1 to 8 are very short-answer questions and carry 1 mark each.
(iii) Question numbers 9 to 18 are short-answer questions and carry 2 marks each.
(iv) Question numbers 19 to 27 are also short-answer questions and carry 3 marks.
(v) Question numbers 28 to 30 are long-answer questions and carry 5 marks each.
(vi) Use Log Tables, if necessary. Use of calculators is not allowed.

  • Question 1
    Give one example each of 'oil in water' and 'water in oil' emulsion. VIEW SOLUTION

  • Question 2
    Which reducing agent is employed to get copper from the leached low-grade copper ore? VIEW SOLUTION

  • Question 3
    Which of the following is a more stable complex and why ?

    CoNH363+ and Coen33+ VIEW SOLUTION

  • Question 4
    Write the IUPAC name of the compound.
                             VIEW SOLUTION

  • Question 5
    Which of the following isomers is more volatile:
    o-nitrophenol or p-nitrophenol? VIEW SOLUTION

  • Question 7
    Arrange the following compounds in increasing order of solubility in water :

  • Question 8
    Which of the two components of starch is water soluble? VIEW SOLUTION

  • Question 9
    An element with density 11.2 g cm–3 forms a f.c.c. lattice with edge length of 4 × 10–8 cm.
    Calculate the atomic mass of the element.
    (Given : NA = 6.022 × 1023 mol–1) VIEW SOLUTION

  • Question 10
    Examine the given defective crystal:

    Answer the following questions :
    (i) What type of stoichiometric defect is shown by the crystal?
    (ii) How is the density of the crystal affected by this defect?
    (iii) What type of ionic substances show such defect? VIEW SOLUTION

  • Question 11
    Calculate the mass of a compound (molar mass = 256 g mol−1) to be dissolved in 75 g of benzene to lower its freezing point by 0.48 K (Kf = 5.12 K kg mol−1). VIEW SOLUTION

  • Question 12
    Define an ideal solution and write one of its characteristics. VIEW SOLUTION

  • Question 13
    Write two differences between 'order of reaction' and 'molecularity of reaction'. VIEW SOLUTION

  • Question 14
    Outline the principles behind the refining of metals by the following methods:
    (i) Zone refining method
    (ii) Chromatographic method VIEW SOLUTION

  • Question 15
    Complete the following chemical equations :
    (i) Ca3P2 + H2O →
    (ii) Cu + H2SO4(conc.) →

    Arrange the following in the order of the property indicated against each set :
    (i) HF, HCl, HBr, HI − increasing bond-dissociation enthalpy.
    (ii) H2O, H2S, H2Se, H2Te − increasing acidic character. VIEW SOLUTION

  • Question 16
    Write the IUPAC name of the complex [Cr(NH3)4Cl2]+. What type of isomerism does it exhibit? VIEW SOLUTION

  • Question 17
    (i) Which alkyl halide from the following pair is chiral and undergoes faster SN2 reaction?

    (ii) Out of SN1 and SN2, which reaction occurs with

    (a) Inversion of configuration
    (b) Racemisation VIEW SOLUTION

  • Question 18
    Draw the structure of major monohalo product in each of the following reactions :



  • Question 19
    (a) In reference to Freundlich adsorption isotherm, write the expression for adsorption of gases on solids in the form of an equation.
    (b) Write an important characteristic of lyophilic sols.
    (c) Based on the type of particles of dispersed phase, give one example each of associated colloid and multimolecular colloid. VIEW SOLUTION

  • Question 20
    (a) Draw the structures of the following molecules:
    (i) XeOF4
    (ii) H2SO4

    (b) Write the structural difference between white phosphorus and red phosphorus. VIEW SOLUTION

  • Question 21
    Account for the following:

    (i) PCl5 is more covalent than PCl3.
    (ii) Iron on reaction with HCl forms FeCl2 and not FeCl3.
    (iii) The two O−O bond lengths in the ozone molecule are equal. VIEW SOLUTION

  • Question 22
    The following data were obtained during the first-order thermal decomposition of SO2Cl2 at a constant volume:
    SO2Cl2(g) → SO2(g) + Cl2(g)
    Experiment Time/s−1 Total pressure/atm
    Calculate the rate constant.
    (Given : log 4 = 0.6021, log 2 = 0.3010) VIEW SOLUTION

  • Question 23
    (i) Give two examples of macromolecules that are chosen as drug targets.
    (ii) What are antiseptics ? Give an example.
    (iii) Why is the use of aspartame limited to cold foods and soft drinks ? VIEW SOLUTION

  • Question 24
    (i) Deficiency of which vitamin causes night-blindness?
    (ii) Name the base that is found in nucleotide of RNA only.
    (iii) Glucose on reaction with HI gives n-hexane. What does it suggest about the structure of glucose? VIEW SOLUTION

  • Question 25
    After the ban on plastic bags, students of a school decided to make people aware of the harmful effects of plastic bags on the environment and Yamuna River. To make the awareness more impactful, they organised a rally by partnering with other schools and distributed paper bags to vegetable vendors, shopkeepers and departmental stores. All the students pledged not to use polythene bags in the future to save the Yamuna River.

    After reading the above passage, answer the following questions:
    (i) What values are shown by the students?
    (ii) What are bio-degradable polymers? Give one example.
    (iii) Is polythene a condensation or an addition polymer? VIEW SOLUTION

  • Question 26
    (a) Write the mechanism of the following reaction :
    CH3CH2OH    HBr    CH3CH2Br+H2O

    (b) Write the equation involved in Reimer-Tiemann reaction. VIEW SOLUTION

  • Question 27
    Give the structures of A, B and C in the following reactions :



    How will you convert the following?
    (i) Nitrobenzene into aniline

    (ii) Ethanoic acid into methanamine

    (iii) Aniline into N−phenylethanamide

    (Write the chemical equations involved.) VIEW SOLUTION

  • Question 28
    (a) Define the following terms :

    (i) Limiting molar conductivity
    (ii) Fuel cell

    (b) Resistance of a conductivity cell filled with 0.1 mol L−1 KCl solution is 100 Ω. If the resistance of the same cell when filled with 0.02 mol L−1 KCl solution is 520 Ω, calculate the conductivity and molar conductivity of 0.02 mol L−1 KCl solution. The conductivity of 0.1 mol L−1 KCl solution is 1.29 × 102 Ω−1 cm−1.

    (a) State Faraday's first law of electrolysis. How much charge in terms of Faraday is required for the reduction of 1 mol of Cu2+ to Cu.

    (b) Calculate emf of the following cell at 298 K:
    Mg(s) | Mg2+(0.1 M) || Cu2+ (0.01) | Cu(s)
    [Given Eocell = +2.71 V, 1 F = 96500 C mol–1] VIEW SOLUTION

  • Question 29
    (a) How do you prepare:
    (i) K2MnO4 from MnO2?
    (ii) Na2Cr2O7 from Na2CrO4?

    (b) Account for the following:
    (i) Mn2+ is more stable than Fe2+ towards oxidation to +3 state.
    (ii) The enthalpy of atomisation is lowest for Zn in 3d series of the transition elements.
    (iii) Actinoid elements show wide range of oxidation states.

    (i) Name the elements of 3d transition series that show maximum number of oxidation states. Why does this happen?
    (ii) Which transition metal of 3d series has positive E° (M2+/M) value and why?
    (iii) Out of Cr3+ and Mn3+, which is a stronger oxidising agent and why?
    (iv) Name a member of the lanthanoid series that is well-known to exhibit +2 oxidation state.
    (v) Complete the following equation:
    MnO4-+8H++5e-  VIEW SOLUTION

  • Question 30
    (a) Write the products of the following reactions:
    (b) Give simple chemical tests to distinguish between the following pairs of compounds:
         (i) Benzaldehyde and Benzoic acid
         (ii) Propanal and Propanone


    (a) Account for the following:
         (i) CH3CHO is more reactive than CH3COCH3 towards reaction with HCN.
         (ii) Carboxylic acid is a stronger acid than phenol.
    (b) Write the chemical equations to illustrate the following name reactions:
         (i) Wolff-Kishner reduction
         (ii) Aldol condensation
         (iii) Cannizzaro reaction VIEW SOLUTION
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