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CBSE Class 12 Chemistry Solved Question Paper 2017

Short Answer Type

21.

Write one difference in each of the following :
Homogeneous catalysis and Heterogeneous catalysis

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22.

Following data are obtained for the reaction :
N₂O₅ → 2NO₂ + ½O₂

t/s	0	300	600
[N₂O₅]/mol L^–1	1.6 × 10^–2	0.8 × 10^–2	0.4 × 10^–2

(a) Show that it follows first order reaction.
(b) Calculate the half-life.
(Given log 2 = 0.3010 log 4 = 0.6021)

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23.

Write the principle of the method used for the refining of germanium.

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24.

Out of PbS and PbCO3 (ores of lead), which one is concentrated by froth flotation process preferably?

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25.

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26.

Give reasons:
Thermal stability decreases from H₂O to H₂Te.

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27.

Give reasons:
Fluoride ion has higher hydration enthalpy than chloride ion.

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28.

Give reasons:
Nitrogen does not form pentahalide.

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29.

Account for the following :
Transition metals form large number of complex compounds.

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30.
Account for the following :
The lowest oxide of transition metal is basic whereas the highest oxide is
amphoteric or acidic.

The lowest oxide of transition metal is basic because of some valence electron are not involved in bonding thus act as a base due to the availability of free electrons. The highest oxide of transition metal electrons of metal is involved in the bonding. Therefore, these electrons are not available for donation. Hence, they are acidic in nature.

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