11.
About $$20$$ $$km$$ above the earth, there is an ozone layer. Which one of the following statements about ozone and ozone layer is true? A
Ozone is a triatomic linear molecule
B
It is harmful as it stops useful radiation
C
It is beneficial to us as it stops $$UV$$ - radiation
D
Conversion of $${O_3}$$ to $${O_2}$$ is an endothermic reaction
Answer :
It is beneficial to us as it stops $$UV$$ - radiation
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Ozone is an allotropic form of oxygen. It is present in the upper atmosphere ( about $$20\,km$$ above the surface of the earth ). It is believed to be formed in the upper atmosphere by the action of $$UV$$ - rays on oxygen as $$3{O_2} + UV{\text{ - rays}} \to 2{O_3},$$ $$\Delta H = 142.7\,kJ\,mo{l^{ - 1}}$$
12.
On adding ammonium hydroxide solution to $${A_2}{\left( {S{O_4}} \right)_3}\left( {aq} \right):$$ A
A precipitate is formed which does not dissolve in excess of ammonium hydroxide
B
A precipitate is formed which dissolves in excess of ammonia solution
C
No precipitate is formed
D
None of these
Answer :
A precipitate is formed which does not dissolve in excess of ammonium hydroxide
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$$\eqalign{
& A{l_2}{\left( {S{O_4}} \right)_3} + 6N{H_4}OH \to 2Al{\left( {OH} \right)_3} + 3{\left( {N{H_4}} \right)_2}S{O_4} \cr
& Al{\left( {OH} \right)_3} + NaOH \to \mathop {N{a^ + }{{\left[ {Al{{\left( {OH} \right)}_4}} \right]}^ - }}\limits_{{\text{Soluble complex}}} \cr
& {\text{It is insoluble in}}\,N{H_4}OH. \cr} $$
13.
Which of the following ion is the most stable? A
$$S{n^{2 + }}$$
B
$$G{e^{2 + }}$$
C
$$S{i^{2 + }}$$
D
$$P{b^{2 + }}$$
Answer :
$$P{b^{2 + }}$$
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14.
$$PC{l_3}$$ reacts with water to form A
$$P{H_3}$$
B
$${H_3}P{O_3},HCl$$
C
$$POC{l_3}$$
D
$${H_3}P{O_4}$$
Answer :
$${H_3}P{O_3},HCl$$
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$$PC{l_3}$$ is easily hydrolysed by water to give $$POC{l_3}$$ and finally it gives $${H_3}P{O_3}$$ and $$HCl.$$
15.
Which one is a property of ozone? A
It acts as an oxidising agent in dry state.
B
It oxidises $$PbS$$ to $$PbS{O_4}.$$
C
It oxidises $$Hg$$ to $$H{g_2}O.$$
D
All of these.
Answer :
All of these.
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16.
Which of the following does not show similarity between boron and aluminium? A
Both form oxides of type $${M_2}{O_3}$$ when heated with oxygen at high temperature.
B
Both dissolve in alkalies and evolve hydrogen.
C
Hydroxides of both the elements are basic in nature.
D
Both form nitrides of $$MN$$ type when heated with $${N_2}.$$
Answer :
Hydroxides of both the elements are basic in nature.
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$$B{\left( {OH} \right)_3}$$ is a weak acid while $$Al{\left( {OH} \right)_3}$$ is amphoteric in nature.
17.
Match the column I with column II and mark the appropriate choice.
Column I
Column II
a.
Used as lubricant
1.
Carbon dioxide
b.
Oxide with three-dimensional structure
2.
Graphite
c.
Used in solar cells
3.
Silica
d.
Anhydride of carbonic acid
4.
Silicon
A
a - 4, b - 3, c - 2, d - 1
B
a - 4, b - 1, c - 3, d - 2
C
a - 3, b - 2, c - 1, d - 4
D
a - 2, b - 3, c - 4, d - 1
Answer :
a - 2, b - 3, c - 4, d - 1
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18.
The product formed in the reaction of $$SOC{l_2}$$ with white
phosphorous is A
$$PC{l_3}$$
B
$$S{O_2}C{l_2}$$
C
$$SC{l_2}$$
D
$$POC{l_3}$$
Answer :
$$PC{l_3}$$
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$${P_4} + 8SOC{l_2} \to 4PC{l_3} + 4S{O_2} + 2{S_2}C{l_2}$$
19.
Strongest hydrogen bonding is shown by A
water
B
ammonia
C
$$HF$$
D
hydrogen sulphide
Answer :
$$HF$$
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$$HF$$ has strongest hydrogen bonding due to the fact that it have small size and high electronegativity.
20.
The oxidation states of sulphur in the anions $$SO_3^{2 - },{S_2}O_4^{2 - }$$ and $${S_2}O_6^{2 - }$$ follows the order A
$${S_2}O_4^{2 - } < {S_2}O_6^{2 - } < SO_3^{2 - }$$
B
$${S_2}O_6^{2 - } < {S_2}O_4^{2 - } < SO_3^{2 - }$$
C
$${S_2}O_4^{2 - } < SO_3^{2 - } < {S_2}O_6^{2 - }$$
D
$$SO_3^{2 - } < {S_2}O_4^{2 - } < {S_2}O_6^{2 - }$$
Answer :
$${S_2}O_4^{2 - } < SO_3^{2 - } < {S_2}O_6^{2 - }$$
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$$\eqalign{
& {\text{Oxidation state of }}S{\text{ in}}\,\,SO_3^{2 - } \cr
& x + \left( { - 2 \times 3} \right) = - 2, \cr
& x = + 6 - 2 = + 4 \cr
& {\text{Oxidation state of }}S{\text{ in}}\,\,{S_2}O_4^{2 - } \cr
& 2x + \left( { - 2 \times 4} \right) = - 2 \cr
& 2x = + 8 - 2 = + 6 \cr
& x = \frac{{ + 6}}{2} = + 3 \cr
& {\text{Oxidation state of }}S{\text{ in}}\,\,{S_2}O_6^{2 - } \cr
& 2x + \left( { - 2 \times 6} \right) = - 2 \cr
& 2x = + 12 - 2 = 10 \cr
& x = \frac{{10}}{2} = + 5 \cr} $$