Subject

Chemistry

Class

ICSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type

11.

Answer the following:
Define Raoult’s law for the elevation of the boiling point of a solution.

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12.

An ionic compound is made up of A cations and B anions. If A cations are present at the alternate corners and B anion is present on the body of the diagonal, what is the formula of the ionic compound?

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13.

What will be the vapour pressure of a solution containing 5 moles of sucrose (C12H22O11) in 1 kg of water, if the vapour pressure of pure water is 4.57 mm ofHg?
[C = 12, H = 1, O = 16]


We know that
fraction numerator straight P subscript water superscript 0 space minus space straight P subscript solution superscript 0 over denominator straight P subscript water superscript 0 end fraction space equals space straight X subscript sucrose
therefore

straight X subscript sucrose space equals space fraction numerator straight n subscript 2 over denominator straight n subscript 1 plus straight n subscript 2 end fraction space equals space fraction numerator 5 over denominator 5 plus begin display style 1000 over 18 end style end fraction space equals fraction numerator space 5 over denominator 60.5 end fraction space equals space 0.083

therefore fraction numerator space straight P to the power of 0 minus straight P over denominator straight P to the power of 0 end fraction space equals space 0.083

straight P to the power of 0 minus straight P space equals space 0.083 space straight x space straight P to the power of 0 space equals space 0.083 space straight x space 4.57 space equals space 0.38

therefore space straight P equals space straight P to the power of 0 minus 0.38 space equals space 4.57 minus 038 space equals space 4.19 space mm space of space Hg

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14.

A 2 molal solution of sodium chloride in water causes an elevation in the boiling point of water by 1.88 K. What is the value of Van’t Hoff factor? What does it signify? [Kb = 0.52 K kg mol-1]

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15.

(i) Write the mathematical expression relating the variation of rate constant of a reaction with temperature.

(ii) How can you graphically find the activation energy of the reaction from the above expression?

(iii) The slope of the line in the graph of log k (k = rate constant) versus 1/T is – 5841. Calculate the activation energy of the reaction.

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16.

Define Frenkel defect in solid crystal.

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17.

Explain giving reasons why: 
 Ionic solids conduct electricity in molten state, but not in solid state.

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18.

Explain giving reason:
Solution of sodium chloride has no effect on litmus, but a solution of zinc chloride turns blue litmus red.

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19.

In a crystal of diamond: 
(i) How many carbon atoms are present per unit cell?
(ii) What type of lattice does diamond crystallize in?
(iii) How many carbon atoms surround each carbon atom?
(iv) How are they arranged?

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20.

(i) What is standard hydrogen electrode? 

(ii) 0.05 M NaOH solution offered a resistance of 31.6 ohm in a conductivity cell at 298 K. If the cell constant of the cell is 0.367 cm-1, calculate the molar conductivity of the NaOH solution.

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