CBSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type



Write the structures of A, B and C in the following:

straight i right parenthesis space straight C subscript 6 straight H subscript 5 space minus CONH subscript 2 space rightwards arrow with Br subscript 2 divided by aq. KOH on top space straight A space rightwards arrow from 0 minus 5 to the power of 0 straight C to NaNO subscript 2 space plus HCl of space straight B space rightwards arrow with KI on top space straight C

ii right parenthesis space CH subscript 3 minus Cl space rightwards arrow with KCN on top space straight A space rightwards arrow with LiAlH subscript 4 on top space straight B rightwards arrow from increment to CHCl subscript 3 space plus alc. space KOH of space straight C



(i) What is the role of t-butyl peroxide in the polymerization of ethene?

(ii) Identify the monomers in the following polymer:

(iii)Arrange the following polymers in the increasing order of their intermolecular forces:
Polystyrene, Terylene, Buna-S


Write the mechanism of free radical polymerization of ethene.



Due to hectic and busy schedule, Mr. Angad made his life full of tensions and anxiety. He started taking sleeping pills to overcome the depression without consulting the doctor. Mr. Deepak, a close friend of Mr. Angad, advised him to stop taking sleeping pills and suggested to change his lifestyle by doing Yoga, mediation and some physical exercise. Mr. Angad followed his friend's advice and after few days he started feeling better.
After reading the above passage, Ans the following:

(i)What are the values (at least two) displayed by Mr. Deepak?
(ii)Why is it not advisable to take sleeping pills without consulting a doctor?
(iii)What are tranquillizers? Give two examples.


 Multiple Choice QuestionsLong Answer Type


a) Calculate the freezing point of the solution when 1.9 g of MgCl2 (M = 95 g mol−1) was dissolved in 50 g of water, assuming MgCl2 undergoes complete ionization.
 (Kf for water = 1.86 K kg mol−1)

(i) Out of 1 M glucose and 2 M glucose, which one has a higher boiling point and why?
(ii) What happens when the external pressure applied becomes more than the osmotic pressure of solution?


(a)When 2.56 g of sulphur was dissolved in 100 g of CS2, the freezing point lowered by 0.383 K. Calculate the formula of sulphur (Sx).
(Kf for CS2 = 3.83 K kg mol−1, Atomic mass of sulphur = 32 g mol−1]

(b)Blood cells are isotonic with 0.9% sodium chloride solution. What happens if we place blood cells in a solution containing
(i)1.2% sodium chloride solution?
(ii)0.4% sodium chloride solution?



(a) Account for the following:
(i)Ozone is thermodynamically unstable.
(ii)Solid PCl5 is ionic in nature.
(iii)Fluorine forms only one oxoacid HOF.

(b) Draw the structure of
(i) BrF5
(ii) XeF4

(i)Compare the oxidizing action of F2 and Cl2 by considering parameters such as bond dissociation enthalpy, electron gain enthalpy and hydration enthalpy.
(ii)Write the conditions to maximize the yield of H2SO4 by contact process.
(iii)Arrange the following in the increasing order of property mentioned:

(a)H3PO3, H3PO4, H3PO2 (Reducing character)
(b)NH3, PH3, AsH3, SbH3, BiH3 (Base strength)



Write the structures of A, B, C, D and E in the following reactions:


(a)Write the chemical equation for the reaction involved in Cannizzaro reaction.
(b)Draw the structure of the semicarbazone of ethanal.
(c)Why pKa of F-CH2-COOH is lower than that of Cl−CH2−COOH?
(d)Write the product in the following reaction:
CH subscript 3 minus CH equals CH minus CH subscript 2 CN space rightwards arrow from left parenthesis ii right parenthesis space straight H subscript 2 straight O to left parenthesis straight i right parenthesis space DIBAL minus straight H of

(e)How can you distinguish between propanal and propanone?