Subject

Chemistry

Class

CBSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type

11.

Give reasons for the following:
(i) N2 is less reactive at room temperature.

(ii) H2Te is the strongest reducing agent amongst all the hydrides of Group 16 elements.

(iii) Helium is used in diving apparatus as a diluent for oxygen.

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12.

(a) Write the hybridization and shape of the following complexes:

(i) [CoF6]3–

(ii) [Ni (CN)4]2–

(Atomic number: Co = 27, Ni = 28)


(b) Out of NH3 and CO, which ligand forms a more stable complex with a transition metal and why?

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13.

Calculate the freezing point of the solution when 31 g of ethylene glycol (C2H6O2) is dissolved in 500 g of water. (Kf for water = 1.86 K kg mol–1)

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14.

Define the following terms:

(i) Primitive unit cells

(ii) Schottky defect

(iii) Ferromagnetism

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15.

The rate constant of a first order reaction increases from 2 — 10-2 to 4 — 10-2when the temperature changes from 300 K to 310 K. Calculate the energy of activation (Ea).

(log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021)


According to the Arrhenius equation.

K = Ae(-Ea/RT)

From this, we get

We are given that

initial temperature T1=300K

Final temperature T2=310 K

Rate constant at initial temperature, k 1 = 2 x 10-2

Rate constant at final temperature, k2 = 4 x 10-2

Gas constant, R = 8.314 J K-1

Substituting the value, we get

 

Therefore activation energy of the reaction, Ea

= 535985.94 J mol-

= 535.98 kJ mol-1

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16.

Define the following terms:
(i) Brownian movement
(ii) Peptization
(iii) Multimolecular colloids

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17.

Calculate E.M.F. and G for the following cell:
Mg left parenthesis straight s right parenthesis space vertical line Mg to the power of 2 plus end exponent left parenthesis 0.001 space straight M right parenthesis space vertical line vertical line space Cu to the power of 2 plus end exponent left parenthesis 0.0001 space straight M right parenthesis space vertical line Cu space left parenthesis straight s right parenthesis space

Given space colon space straight E subscript open parentheses bevelled Mg to the power of 2 plus end exponent over Mg close parentheses end subscript superscript 0 space equals negative 2.37

straight E subscript open parentheses bevelled Cu to the power of 2 plus end exponent over Cu close parentheses end subscript superscript 0 space equals plus 0.34 space straight V.

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18.

The conductivity of 0.20 mol L-1 solution of KCl is 2.48 x 10-2 S cm-1. Calculate its molar conductivity and degree of dissociation  (K+) = 73.56 S cm2 mol-1 and  (Cl-)= 76.5 S

(b) What type of battery is mercury cell? Why is it more advantageous than dry cell?

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19.

Which would undergo SN1 reaction faster in the following pair?

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20. Write the IUPAC name of the given compound:


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