Subject

Chemistry

Class

CBSE Class 12

Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

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 Multiple Choice QuestionsShort Answer Type

21.

A first-order reaction is 50% completed in 40 minutes at 300 K and in 20 minutes at 320 K. Calculate the activation energy of the reaction.

(Given: log 2 = 0.3010, log 4 = 0.6021, R = 8.314 JK–1 mol–1)


22.

What happens when

A freshly prepared precipitate of Fe(OH)3 is shaken with a small amount of FeCl3 solution?


23.

What happens when

Persistent dialysis of a colloidal solution is carried out?


24.

What happens when

An emulsion is centrifuged?


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25.

For the reaction

2AgCl (s) + H2 (g)  (1 atm)   2 Ag (s) + 2H+ (0.1 M) + 2Cl- (0.1 M),Go = - 43600 J at 25o C

Calculate the e.m.f. of the cell.
[log 10–n = – n]


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26.

Define fuel cell and write its two advantages.


These are voltaic cells in which the reactants are continuously supplied to the electrodes. There are designed to convert the energy from the combustion of a fuel like a hydrogen, methane, methanol, etc directly into electrical energy.
Advantage : -
(1) A fuel cell works with an efficiency of 60 to 70 %
(2) They are pollution free


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27.

Give reasons:

H3POundergoes disproportionation reaction but H3PO4 does not.


28.

Give reason:

When Cl2 reacts with an excess of F2. ClF3 is formed and not FCl3


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29.

Give Reason:

Dioxygen is a gas while Sulphur is a solid at room temperature.


30.

Draw the structures of the following.
(i) XeF4
(ii) HClO3


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