CBSE Question Paper 2016 Class 12 Chemistry

General Instructions:

• All questions are compulsory.
• Questions number 1 to 5 are very short answer questions and carry 1 mark each.
• Questions number 6 to 10 are short answer questions and carry 2 marks each.
• Questions number 11 to 22 are also short answer questions and carry 3 marks each.
• Question number 23 is a value based question and carry 4 marks.
• Questions number 24 to 26 are long answer questions and carry 5 marks each.
• Use log tables, if necessary. Use of calculators is not allowed.

1. Write the structure of an isomer of compound C₄H₉Br which is most reactive towards S_N1 reaction.
2. Pb(NO₃)₂ on heating gives a brown gas which undergoes dimerization on cooling? Identify the gas.
3. Give an example each of a molecular solid and an ionic solid.
4. Write the IUPAC name of the given compound:
   
5. What is the reason for the stability of colloidal sols?
   1. Gas (A) is more soluble in water than Gas (B) at the same temperature.
      Which one of the two gases will have the higher value of K_H (Henry’s constant) and why?
   2. In non-ideal solution, what type of deviation shows the formation of maximum boiling azeotropes ?
6. Write the structures of the following:
   1. BrF₃
   2. XeF₄

   OR

   What happens when:

   1. SO₂ gas is passed through an aqueous solution Fe³⁺salt?
   2. XeF₄ reacts with SbF₅?
7. When a coordination compound CoCl₃.6NH₃ is mixed with AgNO₃, 3 moles of AgCl are precipitated per mole of the compound. Write
   1. Structural formula of the complex
   2. IUPAC name of the complex
8. For reaction: H₂+CI₂2HCI
   Rate=K
   1. Write the order and molecularity of this reaction.
   2. Write the unit of k.
9. Write the chemical equations involved in the following reactions:
   1. Hoffmann-bromamide degradation reaction
   2. Carbylamine reaction
10. An element crystallizes in a b.c.c. lattice with cell edge of 500pm. The density of the element is 7.5g cm^-^3cm^-^3. How many atoms are present in 300 g of the element?
11. For the first order thermal decomposition reaction, the following data were obtained:
    C₂H₅Cl(g)→C₂H₄(g)+HCl(g)

    Time / sec	Total pressure / atm
    0	0.30
    300	0.50

    Calculate the rate constant
    (Given: log 2=0.301, log 3=0.4771, log 4=0.6021)

12. Define the following terms:
    1. Lyophilic colloid
    2. Zeta potential
    3. Associated colloids
    1. Name the method of refining of nickel
    2. What is the role of cryolite in the extraction of aluminium?
    3. What is the role of limestone in the extraction of iron from its oxides?
13. Calculate the boiling point of solution when 4 g of MgSO₄ (M=120 g mol^-1) was dissolved in 100 g of water, assuming MgSO₄ undergoes complete ionization. (K_b for water=0.52 K kg mol^-1)
14. Give reasons:
    1. SO₂ is reducing while TeO₂ is an oxidizing agent.
    2. Nitrogen does not form pentahalide.
    3. ICl is more reactive than I₂.
15. Write the final product (s) in each of the following reactions:
    1. 
    2. 
    3. 
16. Give reasons for the following:
    1. Aniline does not undergo Friedal-Crafts reaction.
    2. (CH₃)₂ NH is more basic than (CH₃)₃N in an aqueous solution.
    3. Primary amines have higher boiling point than tertiary amines.
17. How do you convert:
    

    OR

    Write the major product(s) in the following:

    1. Chlorobenzene to biphenyl
    2. Propene to 1-iodopropane
    3. 2-bromobutane to but-2-ene
    4. 
    5. 
    6. 
    1. What is the role of Sulphur in the vulcanization of rubber?
    2. Identify the monomers in the following polymer:
    3. Arrange the following polymers in the increasing order of their intermolecular forces:
       Terylene, Polythene, Neoprene
    1. Write the structural difference between starch and cellulose.
    2. What type of linkage is present in Nucleic acids?
    3. Give one example each for fibrous protein and globular protein.
    1. For the complex [Fe(H₂O)₆]³⁺, write the hybridization, magnetic character and spin of the complex. (At. number: Fe=26)
    2. Draw one of the geometrical isomers of the complex [Pt(en)₂CI₂]²⁺ which is optically inactive.
18. Due to hectic and busy schedule, Mr. Singh started taking junk food in the lunch break and slowly became habitual of eating food irregularly to excel in his field. One day during meeting he felt severe chest pain and fell down. Mr. Khanna, a close friend of Mr. Singh. took him to doctor immediately. The doctor diagnosed that Mr. Singh was suffering from acidity and prescribed some medicines. Mr. Khanna advised him to eat home made food and change his lifestyle by doing yoga, meditation and some physical exercise. Mr. Singh followed his friend’s advice and after few days he started feeling better. After reading the above passage, answer the following:
    1. What are the values (at least two) displayed by Mr. Khanna?
    2. What are antacids? Give one example.
    3. Would it be advisable to take antacids for a long period of time? Give reason.
    1. Calculate E˚cell for the following reaction at 298K:
       2Al(s)1 3Cu²⁺(0.01M)→2Al³⁺ (0.01M) 1 3Cu(s)
       Given: E_cell = 1.98 V
    2. Using the E˚ values of A and B, predict which is better for coating the surface of iron [E°(Fe²⁺/Fe)=-0.44V] to prevent corrosion and why ?
       Given: E˚(A2+/A)=-2.37V : E° (B²⁺/B)=-0.14V

19. OR

    1. The conductivity of 0.001 molL^-1 solution of CH₃COOH is 3.905X 10^-5S cm^-1 Calculate its molar conductivity and degree of dissociation (∝).
       Given (H⁺)=349.6 S cm² mol^-1 and (CH₃COO^–)=40.9 S cm² mol^-1
    2. Define electrochemical cell. What happens if external potential applied becomes greater than E°_Cell of electrochemical cell?

25. 1. Account for the following:
       1. Mn shows the highest oxidation state of +7 with oxygen but with fluorine it shows the highest oxidation state of +4.
       2. Cr²⁺ is a strong reducing agent.
       3. Cu²⁺ salts are coloured while Zn²⁺ salts are white.
    2. Complete the following equations:
       1. 2MnO₂+4KOH+O₂
       2. CrO+14H⁺+61^-→→

    OR

    1. The elements of 3d transition series are given as:
       Sc Ti V Cr Mn Fe Co Ni Cu Zn
    2. Answer the following:
       1. Write the element which shows maximum number of oxidation states.
          Give reason.
       2. Which element has the highest m.p?
       3. Which element shows only +3 oxidation state?
       4. Which element is a strong oxidizing agent in +3 oxidation state and why?

26. 1. Write the structures of A and B in the following reactions:
       1. CH₃COCl
       2. CH₃MgBr
    2. Distinguish between:
       1. C₆H₅-COCH₃ and C₆H₅-CHO
       2. CH₃COOH and HCOOH
    3. Arrange the following in the increasing order of their boiling points:
       CH₃CHO, CH₃COOH, CH₃C₂OH

    OR

    1. Write the chemical reaction involved in Wolff-Kishner reduction.
    2. Arrange the following in the increasing order of their reactivity towards nucleophilic addition reaction:
       C₆H₅COCH₃, CH₃-CHO, CH₃COCH₃
    3. Why carboxylic acid does not give reactions of carbonyl group?
    4. Write the product in the following reaction
       CH₃CH₂CH=CH₂CH₂CN
    5. A and B are two functional isomers of compound C₃H₆O. On heating with NaOH and I₂, isomer B forms yellow precipitate of iodoform whereas isomer A does not form any precipitate. Write the formulae of A and B.