CBSE SAMPLE QUESTION PAPER Chemistry (Theory) - Class XII (Code C)

 

 

Time : 3 Hours                                                                                                                                            Max. Marks : 70

 

General Instructions :

 

1.         All questions are compulsory.

2.         Questions nos. 1 to 8 are very short answer questions and carry 1 marks each.

3.         Questions nos. 9 to 18 are short answer questions and carry 2 marks each.

4.         Questions nos. 19 to 27 are also short answer questions and carry 3 marks each.

5.         Questions nos. 28 to 30 are long answer questions and carry 5 marks each.

6.         Use log tables if necessary, use of calculators is not allowed.

 

Very Short Answer Type Questions [1×8]

 

1.         Write name of two ores of Cu.

2.         How many compounds of molecular formula C₄H₁₁N will give positive carbyl amine test?

3.         Arrange the given compounds in correct order of acidity: ROH, H₂O,    , RCOOH.

 

4.         Define analgesics.

5.         Sol of Agl is prepared by mixing excess of AgNO₃ and KI. Write the charges present on fixed layer and diffused layer of the sol formed.

6.         Name a reagent used to distinguish between 2-pentanone & pentanal.

7.         Name any two homopolymers.

8.         Name two organic halides which do not under go S_N reaction readily.

 

Short Answer Type Questions          [2×10]

 

9.         In a compound AB, having NaCl type structure atoms touching 1 tetrad axis are removed. Find the formula of left compound.

10.       Write monomers of BuNa – N & its one use.

11.       Copper is not a very electropositive element, yet it is present in form of copper glance in atmosphere & not in metallic state, why?

12.       An organic compound pentamerises in benzene. Calculate the value of van’t Hoff factor (i) for it, if % of pentamerisation is 75%.

13.       Calculate the total number of unit cells in 11.7 g of NaCl.

14.       Calculate time required to deposit 1 mmole of Cu by passage of 9.65 ampere through aqueous solution of copper sulphate, electrolysed taking inert electrodes.

15.       Describe the following with one example.

            Bacteriostatic antibiotics

16.       Give the reaction of glucose which proves

            (i) It has long chain of 6 carbon atoms

            (ii) 5 Alcoholic groups

17.       In zinc blende structure of ZnS, S^2– constitutes ccp lattice & zinc ions are present in tetrahedral voids. Calculate the minimum distance between Zn²⁺ & S^2–, if edge length of unit cell is 212 pm.

18.       Fructose has a ketonic group but it still gives positive test with Tollen’s reagent; Explain.

 

Very Short Answer Type Questions [3×8]

 

19.       Explain why?

            (i)   [NiCl4]^2– is paramagnetic whereas [PtCl4]^2– is diamagnetic?

            (ii)  [Ni(H2O)6]²⁺ is green whereas [Ni(NH₃)₆]²⁺ is violet?

            (iii) Square planar complexes can never show optical activity?

20.       Explain

            (i) Effect of temperature on physisorption & chemisorption.

            (ii) Peptisation, with example.

21.       An organic compound  x (m.f. = C₇H₆O₂), when heated with NH₃ yields product  y , y on treatment with NaOH and Br₂ gives z . Identify x , y  & z .

22.       Justify the products formed in the given reactions

 

            (i)        

 

 

 

 

            (ii)       

 

23.       Explain why?

(i)         Electronic configuration of Hg⁺ is: [xe] 5d¹⁰6s¹, still mercurous salts are diamagnetic.

            (ii)        E⁰Mn³⁺/Mn²⁺ is more positive than E⁰Fe³⁺/Fe²⁺

            (iii)       Magnitudely actinoid contraction is greater than lanthanoid contraction.

24.       Predict the major products of the given reaction

 

            (i)    

 

 

           

            (ii)       

 

 

 

            (iii)      

 

 

 

25. Explain minimum boiling azeotrope with the graph showing their variation from Raoult’s law.

 

Or

 

Equimolal solution of CH₃COONa & Na₂SO₄ are prepared in same amount, If freezing point of Na₂SO₄ solution is –x°C. Calculate freezing point of CH₃COONa (Assuming both the salts are 100% dissociated).

26.       (i)         Explain hybridisation, geometry and shape of

                        XeO₂F₂, SF₄, IF₇

            (ii)        Compare the acidic strength of dioxides of chalcogens

            (iii)       Define transition temperature, with example of sulphur

27.       An electrochemical cell can be represented as

            Pt; H_{2 1atm} | HA₁ || HA₂ | H2 _{(1 atm)}

            If concentration of strong acids HA₁ and HA₂ are 10^–5 M and 10^–3 M respectively. Calculate the emf of the cell.

 

Long Answer Type Questions           [5×3]

 

28.       For any hypothetical reaction

            2x + 3y + z àA

            Experimental result shows:

X(mol/L)          Y(mol/L)          Z(mol/L)           Rate(mol/L/Sec)          

(1)        0.5                      0.5                 0.5                    6X10^-4

(2)        1.5                      0.5                  0.5                    1.8X10^-3

(3)         0.5                      2.0                  0.5                    1.2X10^-3

(4)        1.5                      0.5                  1.5                    1.8X10^-3                             

 

            Find the order of reaction and rate law for give reaction.

Or

While studying the decomposition of N₂O₅ (g) it is observed that a plot of logarithm of its partial pressure versus time is linear. What kinetic parameters can be calculated from it? Explain.

29.       An organic compound (A) (m.f = C₄H₆O₄). When heated with acetic anhydride gives another compound (B) (m.f. = C₄H₄O₃). (B) can be converted back to (A) by hydrolysis. (B) when treated with NH₃ gives compound (C). Identify (A), (B) & (C)

Or

            Starting from benzaldehyde, prepare the following compounds

            (i) Benzophenone

            (ii) 3–phenylpropan-1 ol

            (iii) a-hydroxyphenyl acetic acid

            (iv) Phenyl cyanide

           

(v)                

 

 

30.       Give reasons for the following

            (i)         K₂Cr₂O₇ is preferred to Na₂Cr₂O₇ in volumetric analysis.

            (ii)        He and Ne do not form compounds with fluorine.

            (iii)       During preparation of HI from KI, H₃PO₄ is preferred over H₂SO₄.

            (iv)       For preparing dilute H₂SO₄ water should not be added to conc. H₂SO₄.

            (v)        N₂O supports combustion more vigorously than air.

Or

                        Give the product of reaction of O3 with

            (i)         Hg

            (ii)        K₄[Fe(CN)₆]

            (iii)       S

            (iv)       PbS

            (v)        K₂MnO₄