Subject

Chemistry

Class

ICSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type

11.

Correct the following statements: 

Chloroacetic acid is more acidic than acetic acid because of the - M effect.

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12.

Correct the following statements: 

When acetone is treated with bleaching powder, acetaldehyde is obtained.

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13. The molecular weights of sodium chloride and glucose are determined by the Depression of freezing point method. Compared to their theoretical molecular weights, what will be their observed molecular weights when determined by the above method ? Justify your answer.
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14. An aqueous solution containing 1.70 g of cane sugar in 100 ml water begins to freeze at – 0.093°C. The cryoscopic constant (molal depression constant) of water is 1.86 K Kg mole– 1. Calculate the molecular weight of cane sugar.
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15. A decinormal solution of sodium chloride exerts an osmotic pressure of 4.82 atmosphere at 27°C. Calculate the degree of dissociation of sodium chloride.


Given

π= 4.82 atmosphere, T = 27° C = 27 + 273 = 300 K

C = 0.1, R = 0.821 L atm K– 1 mole– 1

π = i CRT

Or space straight i space equals space straight pi over CRT space equals space fraction numerator 4.82 over denominator 0.1 space straight x space 0.821 space straight x space 300 end fraction space equals space 0.195

space space space space space space space space space space space space space space space space space space space space space space space space space space space space space NaCl space space rightwards arrow space Na to the power of plus space space space space plus space Cl to the power of minus
Initially space space space space space space space space space space space space space space space space space space space space 1 space space space space space space space space space space space 0 space space space space space space space space space space space space 0
At space equ. space space space space space space space space space space space space space space space space space space space 1 minus straight alpha space space space space space space space straight alpha space space space space space space space space space space space straight alpha space
Total space space moles space at space equilibrium space space equals space 1 minus straight alpha space plus straight alpha plus straight alpha
space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals space 1 plus straight alpha

straight i space equals space fraction numerator Observed space no space of space moles space over denominator Normal space no space. of space moles end fraction

straight i space equals space fraction numerator 1 plus straight alpha over denominator 1 end fraction
therefore space straight i space equals space 1 plus straight alpha

space equals 0.195 space equals space 1 space plus straight alpha
straight alpha space equals space 1 minus 0.195 space space equals space 80.5 space equals space 80.5 percent sign

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16. The half life of a radioactive isotope is 10 hours. How many atoms of this isotope will be left after 4 hours if initially 1 gm mole of the radioactive isotope was taken ?  
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17. 90Th234 emits 7alpha particles and 6 beta particles. What will be the atomic number and mass number of the resulting atom.
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18. What is the function of the moderator and the control rod in nuclear reactor ? 
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19.  The melting point of pure silver and pure lead is 961°C and 327°C respectively. A molten mixture of the two metals on cooling at a constant temperature forms a eutectic mixture with a composition of approximately 5% silver and 95% lead at 305°C. Draw a schematic phase diagram for the silver-lead system. Label all the parts of the diagram. Indicate the number of components, phases and degrees of freedom present at the eutectic point.
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20. An aqueous solution of an organic compound contains 10 g of solute per litre. When 1 litre of this solution is treated with 100 ml of ether, 6 g of the organic solute is extracted. How much of the solute will be extracted from the aqueous solution by adding further 100 ml of ether ? (Assume that the molecular state of the solute is the same in ether and water.)
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