Subject

Chemistry

Class

ICSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type

41.

How will you obtain pure potassium permanganate (KMnO4) crystals from its ore, pyrolusite? Give the step involved and the reactions.

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42.

For the reaction:
2 NO left parenthesis straight g right parenthesis space rightwards harpoon over leftwards harpoon space straight N subscript 2 left parenthesis straight g right parenthesis space plus straight O subscript 2 left parenthesis straight g right parenthesis space semicolon increment straight H space equals space minus space heat
straight K subscript straight c space equals space 2.5 space straight x space 10 squared space at space 298 straight K

what will happen to concentration of N2 if:
i) Temperature is decreased to 273K
ii) Pressure is reduced.


i) According to Le Châtelier's principle, an decrease in temperature would shift the equilibrium to right and-and value of Kc increased.

ii) increase or decrease in pressure affect equilibrium only when the number of moles varies. Since the number of moles on both side reactant and product is same hence there will be not any change.

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43.

What will be the value of van't Hoff factor (i) Of benzoic acid if it dimerised in aqueous solution? How will the experimental weight vary as compared to the normal molecular weight? 

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