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Board Paper of Class 12-Science 2017 Chemistry (SET 3) - 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
    What is the effect of catalyst on:   (1)
    (i) Gibbs energy (∆G) and
    (ii) activation energy of a reaction? VIEW SOLUTION

  • Question 2
    Write one similarity between Physisorption and Chemisorption.    VIEW SOLUTION

  • Question 3
    Write the formula of an oxo-anion of Manganese (Mn) in which it shows the oxidation state equal to its group number.  VIEW SOLUTION

  • Question 4
    Write the structure of 3-Bromo-2-methylprop-1-ene.    VIEW SOLUTION

  • Question 5
    Write IUPAC name of the following compound:    
    (CH3)2 N − CH2CH3

  • Question 6
    Write the reactions involved in the following reactions:    
    (i) Clemmensen reduction
    (ii) Cannizzaro reaction VIEW SOLUTION

  • Question 7
    Draw the structures of the following:   
    (i) H4P2O7

  • Question 8
    Define the following terms:  
    (i) Abnormal molar mass
    (ii) van't Hoff factor (i) VIEW SOLUTION

  • Question 9
    Calculate the degree of dissociation (α) of acetic acid if it's molar conductivity (Λm) is 39.05 S cm2 mol−1.   
    Given, λ°(H+) = 349.8 S cm2 mol−1 and λ°(CH3COO) = 40.9 S cm2 mol−1   VIEW SOLUTION

  • Question 10
    Complete the following chemical equations : 

    (i) F2 + 2Cl

    (ii) 2XeF2 + 2H2O →

    What happens when

    (i) HCl is added to MnO2?

    (ii) PCl5 is heated?

    Write the equations involved. VIEW SOLUTION

  • Question 11
    Give reasons :    (1 × 3 = 3)
    (i)   Acetylation of aniline reduces its activation effect.
    (ii)  CH3NH2 is more basic than C6H5NH2.
    (iii) Although –NH2 is o/p directing group, yet aniline on nitration gives a significant amount of m-nitroaniline. VIEW SOLUTION

  • Question 12
    Give reasons: 
    (i) Thermal stability decreases from H2O to H2Te. 
    (ii) Fluoride ion has higher hydration enthalpy than chloride ion. VIEW SOLUTION

  • Question 13
    Define the following:  

    (i) Anionic detergents

    (ii) Limited spectrum antibiotics

    (iii) Tranquilizers VIEW SOLUTION

  • Question 14
    Write the structures of the monomers used for getting the following polymers:   

    (i) Nylon-6

    (ii) Melamine – formaldehyde polymer

    (iii) Teflon VIEW SOLUTION

  • Question 15
    Write structures of compounds A, B and C in each of the following reactions: 

    (i) C6H5BrMg/dry etherA(b) H3O+(a) CO2(g) BPCl5C

    (ii) CH3CN(b) H3O+(a) SnCl2/HCl Adil. NaOHBC

    Do the following conversions in not more than two steps :

    (i) Benzoic acid to benzaldehyde

    (ii) Ethyl benzene to Benzoic acid

    (iii) Propanone to Propene VIEW SOLUTION

  • Question 16
    (a) Write the principle of method used for the refining of germanium. 

    (b) Out of PbS and PbCO3 (ores of lead), which one is concentrated by froth floatation process preferably?

    (c) What is the significance of leaching in the extraction of aluminium? VIEW SOLUTION

  • Question 17
    Following compounds are given to you : 

    2-Bromopentane, 2-Bromo-2-methylbutane, 1-Bromopentane

    (i) Write the compound which is most reactive towards SN2 reaction.

    (ii) Write the compound which is optically active.

    (iii) Write the compound which is most reactive towards β-elimination reaction. VIEW SOLUTION

  • Question 18
    Following data are obtained for reaction : 

    N2O5 → 2NO2 + 1/2O2
    t/s 0 300 600
    [N2O5]/mol L–1 1.6 × 10–2 0.8 × 10–2 0.4 × 10–2

    (a) Show that it follows first order reaction.

    (b) Calculate the half-life.

    (Given log 2 = 0.3010, log 4 = 0.6021)

  • Question 19
    Write one difference between each of the following: 

    (i) Multimolecular colloid and Macromolecular colloid

    (ii) Sol and Gel

    (iii) O/W emulsion and W/O emulsion VIEW SOLUTION

  • Question 20
    (i) What type of isomerism is shown by the complex [Co(en)3]Cl3?  

    (ii) Write the hybridisation and magnetic character of [Co(C2O4)3]3–.
    (At. no. of Co = 27)

    (iii) Write IUPAC name of the following Complex [Cr(NH3)3Cl3]. VIEW SOLUTION

  • Question 21
    (a) Calculate the mass of Ag deposited at cathode when a current of 2 amperes was passed through a solution of AgNO3 for 15 minutes.  
    (Given : Molar mass of Ag = 108 g mol−1, 1 F = 96500 C mol−1)

    (b) Define fuel cell VIEW SOLUTION

  • Question 22
    A 10% solution (by mass) of sucrose in water has freezing point of 269.15 K. Calculate the freezing point of 10% glucose in water, if freezing point of pure water is 273.15 K.  

    Given : (Molar mass of sucrose = 342 g mol−1)
        (Molar mass of glucose = 180 g mol−1)

  • Question 23
    After watching a programme on TV about the presence of carcinogens (cancer causing agents) Potassium bromate and Potassium iodate in bread and other bakery products, Ritu a class XII student decided to aware others about the adverse effects of these carcinogens in foods. She consultanted the school principal and requested him to instruct canteen contractor to stop selling sandwiches, pizza, burgers and other bakery products to the students. Principal took an immediate action and instructed the canteen contractor to replace the bakery products with some proteins and vitamins rich food like fruits, salads, sprouts etc. The decision was welcomed by the parents and students.
    After reading the above passage, answer the following questions:   (4)
    (i)  What are the values (at least two) displayed by Ritu?
    (ii)  Which polysaccharide component of carbohydrates is commonly present in bread?
    (iii) Write the two types of secondary structure of proteins.
    (iv) Give two examples of water soluble vitamins. VIEW SOLUTION

  • Question 24
    (a) An element has atomic mass 93 g mol–1 and density 11.5 g cm–3. If the edge length of its unit cell is 300 pm, identify the type of unit cell.

    (b) Write any two differences between amorphous solids and crystalline solids.

    (a) Calculate the number of unit cells in 8.1 g of aluminium if it crystallizes in a f.c.c. structure. (Atomic mass of Al = 27 g mol–1)

    (b) Give reasons:

    (i) In stoichiometric defects, NaCl exhibits Schottky defect and not Frenkel defect.

    (ii) Silicon on doping with Phosphorous forms n-type semiconductor.

    (iii) Ferrimagnetic substances show better magnetism than antiferromagnetic substances. VIEW SOLUTION

  • Question 25
    (a) Write the product(s) in the following reactions : 


    (iii) CH3-CH=CH-CH2-OH PCC?

    (b) Give simple chemical tests to distinguish between the following pairs of compounds :
    (i) Ethanol and Phenol

    (ii) Propanol and 2-methylpropan-2-ol

    (a) Write the formula of reagents used in the following reactions :
    (i) Bromination of phenol to 2,4,6-tribromophenol

    (ii) Hydroboration of propene and then oxidation to propanol.

    (b) Arrange the following compound groups in the increasing order of their property indicated :
    (i) p-nitrophenol, ethanol, phenol (acidic character)

    (ii) Propanol, Propane, Propanal (boiling point)

    (c) Write the mechanism (using curved arrow notation) of the following reaction :


  • Question 26
    (a) Account for the following :  
    (i) Transition metals form large number of complex compounds.
    (ii) The lowest oxide of transition metal is basic whereas the highest oxide is amphoteric or acidic.
    (iii) E° value for the Mn3+/Mn2+ couple is highly positive (+1.57 V) as compare to Cr3+/Cr2+.
    (b) Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.
    (a) (i) How is the variability in oxidation states of transition metals different from that of the p-block elements?   
    (ii) Out of Cu+ and Cu2+, which ion is unstable in aqueous solution and why?
    (iii) Orange colour of Cr2O72– ion changes to yellow when treated with an alkali. Why?
    (b) Chemistry of actinoids is complicated as compared to lanthanoids. Give two reasons.
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