1 Marks Question

Question 11 Mark

ZnO becomes yellow on heating. Why?

Answer

Due to Frenkal defect, ZnO loses its oxygen on heating and turns yellow in colour.
$ ZnO_{(s)} \xrightarrow{Heat} Zn^{2+} + \frac{1}{2}O_{2} + 2e^{-} $

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Question 21 Mark

Out of KCl and AgCl which one shows schottky defect and why?

Answer

KCl shows Schottky defect because its cations and anions are of similar size.

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Question 31 Mark

An element crystallizes in fcc lattice with a cell edge of 300 pm. The density of the element is 10.8 g $ cm^{-3} $. Calculate the number in 108 g of the element.

Answer

We know $d=\frac{ ZM }{a^3 N}$ $\left[\begin{array}{l}m=\text { mass of atom } \\ N=\text { number of atom }\end{array}\right]$
$\therefore \quad N =\frac{108 \times 4}{10.8 \times 27 \times 10^{-24}}$
$=1.48 \times 10^{24}$ atoms

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Question 41 Mark

Analysis shows that FeO has a non-stoichiometric composition with formula $ Fe_{0.95}O $. Give reason.

Answer

It shows metal deficiency defect. In the crystals of FeO, some of $ Fe^{2+} $ cations are replaced by $ Fe^{3+} $ ions. Eventually there would be less amount of metal as compared to stoichiometric composition.

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Question 51 Mark

Glass is assumed to be supercooled liquid. Why?

Answer

Glass is an amorphous solid and if has tendency to flow but, slowly. Hence it is called a supercooled liquid.

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Question 61 Mark

How is ferromagnetism different from paramagnetism?

Answer

Ferromagnetic substances are strongly attracted by the magnetic field and they can be converted into permanent magnet. Paramagnetic substances are weakly attracted by the magnet. They cannot be converted into permanent magnet.

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Question 71 Mark

Which type of stoichiometric crystal defect is found in the following?
(i) ZnS (ii) AgBr

Answer

(i) Frenkel defect,
(ii) Frenkel and Schottky both defects.

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Question 81 Mark

Classify the following into n-type and p-type semiconductors:
(i) Ge doped with In
(ii) B doped with Si.

Answer

(i) n-type semiconductor
(ii) p -type semiconductor.

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Chemistry 1 Marks Question

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