CBSE Board Class 12 Chemistry Sample Papers 2008

General Instructions


i.All questions are compulsory.
ii.The question paper consists of thirty questions divided into 4 sections A, B, C and D. Section A comprises of ten questions of 01 mark each, Section B comprises of five questions of 02 marks each, Section C comprises ten questions of 03 marks each and Section D comprises of five questions of 06 marks each.
iii.All questions in Section A are to be answered in one word, one sentence or as per the exact requirement of the question.
iv.There is no overall choice. However, internal choice has been provided in one question of 02 marks each, three questions of 03 marks each and two questions of 06 marks each. You have to attempt only one of the alternatives in all such questions.
v.In question on construction, drawing should be near and exactly as per the given measurements.
vi.Use of calculators is not permitted.

Question: What is the coordination number of each type of ions in a rock-salt type crystal structure?                                                               (MARKS 1)

Question: Define the term ‘order of reaction’ for chemical reactions.
             (MARKS 1)

Question: What causes Brownian movement in a colloidal solution?
             (MARKS 1)

Question: In which one of the two structures, NO2+and NO2- , the bond angle has a higher value?                                                         (MARKS 1)

Question: Write the IUPAC name of the following compound:         (MARKS 1)

                           

Question: Arrange the following compounds in an increasing order of their acid strengths:                                                                          (MARKS 1)
(CH3)2 CHCOOH, CH3 CH2 CH (Br) COOH, CH3 CH (Br) CH2 COOH
                       
Question: Write a chemical reaction in which the iodide ion replaces the diazonium group I a diazonium salt.                                            (MARKS 1)

Question: Name a substance that can be used as an antiseptic as well as a disinfectant.                                                                            (MARKS 1)

Question: Explain as to why haloarenes are much less reactive than haloalkanes towards nucleophillic substitution reactions.             (MARKS 1)

Question: Which compound in each of the following pairs will react faster in SN2 reaction with -OH? Why?                                                  (MARKS 1)
(i)CH3 Br or CH3 I
(ii)(CH3)3 CCl or CH3Cl

Question: (a) State the IUPAC name of the following compound: (MARKS 2)


(b) Complete the following chemical equations:
CH3 CH2 CH=CH2 + HBr     Peroxide                  . . . . . . . . . . .


Question: State Henry's law correlating the pressure of a gas and its solubility in a solvent and mention two applications for the law.     (MARKS 2)


Question: A first order decomposition reaction takes 40 minutes for 30% decomposition. Calculate its t ½ value.                                        (MARKS 2)

Question: What is meant by the 'rate constant, k' of a reaction? If the concentration be expressed in mol L-1 units and time in seconds, what would be the units for k(i) for a zero order reaction and (ii) for a first order reaction?                                                                                  (MARKS 3)

Question: Define the following terms in relation to proteins:   (MARKS 3)
i.Peptide linkage
ii.Denaturation

Question: List the reactions of glucose which cannot be explained by its open chain structure.                                                                         (MARKS 3)  

Question: Assign a reason for each of the following statement:
(i) Ammonia is a stronger base than phosphine.
(ii) Sulphur in vapour state exhibits a paramagnetic behavior.       (MARKS 3)

Question: Draw the structures of the following molecules:           (MARKS 3)
(i)SF4
(ii)XeF4

Question: What are biodegradable and non-biodegradable detergents? Give one example of each class.                                                      (MARKS 3)

Question: What is   semiconductor?   Describe the two main types   of semiconductors   and   explain mechanisms for their conduction. (MARKS 3)

Question: Calculate the temperature at which a solution 54g of glucose,
(CeH12O6), in 250g of water will freeze.
(Kf for water = 1.86 k mol-1 kg)                                               (MARKS 3)

Question: What are lyophilic and lyophobic sols? Give one example of each type. Which one of these two types of sols is easily coagulated and why?
                     (MARKS 3)

Question: State briefly the principles which serve as basis for the following operations in metallurgy:                                                         (MARKS 3)
     (i)     Froth floatation process
     (ii)    Zone refining
(iii)Reining by liquation
(iv)

Question: Write chemical equations for the following processes:(MARKS 6)
(i)Chlorine reacts with a hot concentrated solution of sodium hydroxide
(ii)Orthophosphorous acid is heated
(iii)PtF6 and xenon are mixed together


Question: Complete the following chemical equations:               (MARKS 6)
(i)     Ca3P2(s) + H2O (1) ? . . . . . . .
(ii)    Cu2+ (aq) + NH2 (aq) ? . . . . . . . 
(iii)   F2 (g) + H2O (1) ? . . . . . . . 

Question: (a) What is a ligand? Give an example of a bidentate ligand.
(b) Explain as to how the two complexes of nickel, [Ni (CN) 4]2- and Ni (CO)4, have different structures but do not differ in their magnetic behavior.
(Ni = 28)                                                              (MARKS 6)

Question:  Name the reagents which are used in the following conversions:
(i)A primary alcohol to an aldehyde
(ii)Butan-2-one to butan-2-ol
(iii)Phenol to 2, 4, 6-tribtomophenol                                          (MARKS 6)

Question:  Account for the following observations:                        (MARKS 6)
(i)pKb for aniline is more than that for methylamine.
(ii)Methylamine solution in water reacts with ferric chloride solution to give a precipitate of ferric hydroxide.
(iii)Aniline does not undergo Friedel-Crafts reaction.

Question: Write the names and structures of the monomers of the following polymers:                                    (MARKS 6)

(i)Buna-S
(ii)Neoprene
(iii)Nylon-6

Question: Conductivity of 0.00241M acetic acid solution is 7.896X 10-5 Scm-1. Calculate its molar conductivity in this solution. If ^m0 for acetic acid be 390.5 S cm2 mol-1, what would be its dissociation constant?    (MARKS 6)


Question: Three electrolytic cells A, B and C containing solutions of zinc sulphate, silver nitrate and copper sulphate, respectively are connected in series. A steady current of 1.5 ampere was passed through them until 1.45g of silver were deposited at the cathode of cell B. How long did the current flow? What mass of copper and what mass of zinc were deposited in the concerned cells? (Atomic masses of Ag = 108, Zn = 65.4, Cu = 63.5)
             (MARKS 6)

Question: Assign reasons for the following:                                 (MARKS 6)
(i)The enthalpies of atomisation of transition elements are high.
(ii)The transitions metals and many of their compounds act as good catalyst.
(iii)From element to element the actinoid contraction is greater than the lanthanoid contraction.

Question: (a) What may be the possible oxidation states of the transition metals with the following d electronic configuration in the ground state of their atoms:                                                                           (MARKS 6)
3d3 4s2, 3d54s2 and 3d64s2. Indicate relative stability of oxidation states in each case.
(b) Write steps involved in the preparation of (i) Na2 CrO4 from chromite ore and (ii) K2MnO4 from pyrolusite ore.

Question: (a) Complete the following reaction statements by giving the missing starting material, reagent or product as requires:            (MARKS 6)
(i)
(ii)
(iii)
(b) Describe the following reactions:
(i) Cannizaro reaction
(ii) Cross aldol condensation

Question:  (a) How would you account for the following:         (MARKS 6)
(i)Aldehydes are more reactive than ketones towards nucleophiles.
(ii)The boiling points of aldehydes and ketones are lower than of the corresponding acids.
(iii)The aldehydes and ketones undergo a number of addition reactions.
(a)Give chemical tests to distinguish between:
(i)Acetaldehyde and benzldehyde
(ii)Propanone and propanol