Subject

Chemistry

Class

CBSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type

31.

Account for the following :
E° value for the Mn3+/Mn2+ couple is highly positive (+1.57 V) as compared to Cr3+/Cr2+.

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32.

Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.


Similarities between lanthanides and actinides

  1. Both have a prominent oxidation state of +3.
  2. They are involved in the filling of (n-2) f orbitals.
  3. They are highly electropositive and very reactive in nature.

Differences between lanthanides and actinides

  1. Lanthanoids are involved in the filling of 4f- orbitals whereas actinoids are involved in the filling of 5f-orbitals.
  2. The binding energy of 4f electrons is comparatively less than that of 5f-electrons. The shielding effect of 5f-electrons is less effective as compared to that of 4f-electrons.
  3. The paramagnetic properties of lanthanoids can be easily explained but this explanation is difficult in the case of actinoids.
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33.

How is the variability in oxidation states of transition metals different from that of the p-block elements?

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34.

Out of Cu+ and Cu2+, which ion is unstable in aqueous solution and why?

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35.

The Orange colour of Cr2O72– ion changes to yellow when treated with an
alkali. Why ?

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36.

Chemistry of actinoids is complicated as compared to lanthanoids. Give two reasons.

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37.

An element has atomic mass 93 g mol–1 and density 11.5 g cm–3. If the edge
the length of its unit cell is 300 pm, identify the type of unit cell.

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38.

Write any two differences between amorphous solids and crystalline solids.

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39.

Calculate the number of unit cells in 8.1 g of aluminium if it crystallizes in a
f.c.c. structure. (Atomic mass of Al = 27 g mol–1)

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40.

Give reasons :
In stoichiometric defects, NaCl exhibits Schottky defect and not Frenkel
defect.

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