Board Paper of Class 12-Science 2017 Chemistry (SET 2) - Solutions

• Question 1
  Write one similarity between Physisorption and Chemisorption.    VIEW SOLUTION

• Question 2
  Write the structure of 2,4-dinitrochlorobenzene.    VIEW SOLUTION

• Question 3
  For a reaction $\mathrm{R}\underset{}{\overset{ }{\to }}\mathrm{P}$, half-life (t_1/2) is observed to be independent of the initial concentration of reactants. What is the order of reaction?     VIEW SOLUTION

• Question 4
  Write IUPAC name of the following compound:  

  CH₃NHCH(CH₃)₂

  VIEW SOLUTION

• Question 5
  Write the formula of an oxo-anion of Chromium (Cr) in which it shows the oxidation state equal to its group number.    VIEW SOLUTION

• Question 6
  Calculate the degree of dissociation (α) of acetic acid if it's molar conductivity (Λ_m) 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 7
  Draw the structures of the following:  
  (i) H₃PO₂
  (ii) XeF₄ VIEW SOLUTION

• Question 8
  Define the following terms:   
  (i) Ideal solution
  (ii) Molarity (M) VIEW SOLUTION

• Question 9
  Complete the following reactions : 
  
  (i) Cl₂ + H₂O →
  
  (ii) XeF₆ + 3H₂O →
   

  OR

  
  What happens when
  
  (i) conc. is H₂SO₄ added to Cu?
  
  (ii) SO₃ is passed through water?
  
  Write the equations. VIEW SOLUTION

• Question 10
  Write the reactions involved in the following:  
  
  (i) Hell-Volhard Zelinsky reaction
  
  (ii) Decarboxylation reaction VIEW SOLUTION

• Question 11
  Write one difference in each of the following:    (3)
  (i) Lyophobic sol and Lyophilic sol
  (ii) Solution and Colloid
  (iii) Homogeneous catalysis and Heterogeneous catalysis VIEW SOLUTION

• Question 12
  Following compounds are given to you : 
  
  2-Bromopentane, 2-Bromo-2-methylbutane, 1-Bromopentane
  
  (i) Write the compound which is most reactive towards S_N2 reaction.
  
  (ii) Write the compound which is optically active.
  
  (iii) Write the compound which is most reactive towards β-elimination reaction. VIEW SOLUTION

• Question 13
  Write the principles of the following methods : 
  
  (i) Vapour phase refining
  
  (ii) Zone refining
  
  (iii) Chromatography VIEW SOLUTION

• Question 14
  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)

  VIEW SOLUTION

• Question 15
  Define the following : 
  
  (i) Cationic detergents
  
  (ii) Narrow spectrum antibiotics
  
  (iii) Disinfectants VIEW SOLUTION

• Question 16
  (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 17
  (i) What type of isomerism is shown by the complex [Co(NH₃)₆] [Cr(CN)₆]?  
  (ii) Why a solution of [Ni(H₂O)₆]²⁺ is green while a solution of [Ni(CN)₄]²⁻ is colourless? (At. no. of Ni = 28)
  (iii) Write the IUPAC name of the following complex : [Co(NH₃)₅(CO₃)]Cl.     VIEW SOLUTION

• Question 18
  Write structures of compounds A, B and C in each of the following reactions: 
  
  (i) ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{Br}\stackrel{\mathrm{Mg}/\mathrm{dry} \mathrm{ether}}{\to }\mathrm{A}\underset{\left(\mathrm{b}\right) {\mathrm{H}}_3{\mathrm{O}}^{+}}{\overset{\left(\mathrm{a}\right) {\mathrm{CO}}_{2\left(\mathrm{g}\right)} }{\to }}\mathrm{B}\stackrel{\mathrm{PC}{l}_5}{\to }\mathrm{C}$
  
  (ii) ${\mathrm{CH}}_3\mathrm{CN}\underset{\left(\mathrm{b}\right) {\mathrm{H}}_3{\mathrm{O}}^{+}}{\overset{\left(\mathrm{a}\right) \mathrm{SnC}{l}_2/\mathrm{HC}l }{\to }}\mathrm{A}\stackrel{\mathrm{dil}. \mathrm{NaOH}}{\to }\mathrm{B}\stackrel{∆}{\to }\mathrm{C}$
   

  OR

  
  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 19
  Write the structures of the monomers used for getting the following polymers: 
  
  (i) Neoprene
  
  (ii) Melamine-formaldehyde polymer
  
  (iii) Buna-S VIEW SOLUTION

• Question 20
  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)

  VIEW SOLUTION

• Question 21
  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 22
  Give reasons: 
  (i) Thermal stability decreases from H₂O to H₂Te. 
  (ii) Fluoride ion has higher hydration enthalpy than chloride ion. VIEW SOLUTION

• 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) Write the product(s) in the following reactions : 
   

  (i)
  
  (ii)
  
  (iii) ${\mathrm{CH}}_3-\mathrm{CH}=\mathrm{CH}-{\mathrm{CH}}_2-\mathrm{OH} \stackrel{\mathrm{PCC}}{\to }?$

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

  (i) Ethanol and Phenol
  
  (ii) Propanol and 2-methylpropan-2-ol

   

  OR

  
  (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 :
  
  VIEW SOLUTION

• Question 25
  (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.

  OR

  (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 Cr₂O₇^2– ion changes to yellow when treated with an alkali. Why?

  (b) Chemistry of actinoids is complicated as compared to lanthanoids. Give two reasons.

  VIEW SOLUTION

• Question 26
  (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.
   

  OR

  
  (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