P - Block Elements MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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41.
Which oxide of nitrogen is obtained on heating ammonium nitrate at $${250^ \circ }C?$$
C
Among halide ions, iodide is the most powerful reducing agent
D
Fluorine is the only halogen that does not show a variable oxidation state
Answer :
$$HF$$ is a stronger acid than $$HCl$$
Due to strong $$H—F$$ bond, $${H^ + }$$ ions are not easily removed due to higher electronegativity $$(EN)$$ of $$F.$$
Hence more bond dissociation energy required.
$${\text{Acidic}}\,{\text{nature}} \propto \frac{1}{{{\text{Bond}}\,{\text{dissociation}}\,{\text{energy}}}}$$
So, $$HF$$ is not a stronger acid than $$HCl.$$
43.
Which of the following is incorrect for white and red phosphorus ?
A
They are both soluble in $$C{S_2}.$$
B
They can be oxidised by heating in air.
C
They consist of the same kind of atoms.
D
They can be converted into one another.
Answer :
They are both soluble in $$C{S_2}.$$
Both white and red phosphorus are not soluble in $$C{S_2}$$ only white phosphorus is soluble in $$C{S_2}.$$
44.
The formation of the oxide ion $${O^{2 - }}\left( g \right),$$ from oxygen atom requires first an exothermic and then an endothermic step as shown below,
$$O\left( g \right) + {e^ - } \to {O^ - }\left( g \right);$$ $${\vartriangle _f}{H^ \circ } = - 141\,kJmo{l^{ - 1}}$$
$${O^ - }\left( g \right) + {e^ - } \to {O^{2 - }}\left( g \right);$$ $${\vartriangle _f}{H^ \circ } = \, + 780\,kJmo{l^{ - 1}}$$
Thus, process of formation of $${O^{2 - }}$$ in gas phase is unfavourable even though $${O^{2 - }}$$ is isoelectronic with neon. It is due to the fact that
A
electron repulsion outweighs the stability gained by achieving noble gas configuration
B
$${O^ - }$$ ion has comparatively srnaller size than
oxygen atom
C
Oxygen is more electronegative
D
addition of electron in oxygen result in large size of the ion
Answer :
electron repulsion outweighs the stability gained by achieving noble gas configuration
Since, electron repulsion predominate over the stability gained by achieving noble gas configuration. Hence, formation of $${O^{2 - }}$$ in gas phase is unfavourable.
45.
Which of the following statements is not correct about the structure of $$PC{l_5}?$$
A
$$PC{l_5}$$ has a square pyramidal structure.
B
Three equatorial $$P - Cl$$ bonds are equivalent.
C
The two axial bonds are different and longer than equatorial bonds.
D
In solid state it exists as $${\left[ {PC{l_4}} \right]^ + }{\left[ {PC{l_6}} \right]^ - }.$$
Answer :
$$PC{l_5}$$ has a square pyramidal structure.
$$PC{l_5}$$ has a trigonal bipyramidal structure.
46.
Match the column I with column II and mark the appropriate choice.
Column I
Column II
a.
Thiosulphuric acid
1.
$${H_2}S{O_5}$$
b.
Caro's acid
2.
$${H_2}{S_2}{O_6}$$
c.
Marshall's acid
3.
$${H_2}{S_2}{O_3}$$
d.
Dithionic acid
4.
$${H_2}{S_2}{O_8}$$
A
a - 1, b - 2, c - 3, d - 4
B
a - 4, b - 3, c - 2, d - 1
C
a - 3, b - 1, c - 4, d - 2
D
a - 2, b - 3, c - 1, d - 4
Answer :
a - 3, b - 1, c - 4, d - 2
No explanation is given for this question. Let's discuss the answer together.
47.
Which of the following is the correct statement about silicones?
A
They are made up of $$SiO_4^{4 - }$$ units.
B
They are polymers made up of $${R_2}SiO$$ units.
C
They are water soluble compounds.
D
They are hydrophilic in nature.
Answer :
They are polymers made up of $${R_2}SiO$$ units.
No explanation is given for this question. Let's discuss the answer together.
48.
When excess of carbon dioxide is passed through lime water, the milkiness first formed disappears due to
A
the reversible reaction taking place
B
formation of water soluble calcium bicarbonate
C
huge amount of heat evolved during the reaction
D
formation of water soluble complex of calcium
Answer :
formation of water soluble calcium bicarbonate
When excess of carbon dioxide is passed in lime water, calcium carbonate is converted to calcium bicarbonate which is soluble, hence the milkiness due to calcium carbonate disappears.
49.
The structure of white phosphorus is
A
square planar
B
pyramidal
C
tetrahedral
D
trigonal planar
Answer :
tetrahedral
No explanation is given for this question. Let's discuss the answer together.
50.
Boric acid is an acid because its molecule
A
contains replaceable $${H^ + }$$ ion
B
gives up a proton
C
accepts $$O{H^ - }$$ from water releasing proton
D
combines with proton from water molecule
Answer :
accepts $$O{H^ - }$$ from water releasing proton
Boric acid can be considered as an acid because its molecule accepts $$O{H^ - }$$ from water, releasing proton.
\[\underset{\text{Acid}}{\mathop{{{H}_{3}}B{{O}_{3}}}}\,+\underset{\text{Base}}{\mathop{{{H}_{2}}O}}\,\rightleftharpoons \underset{\begin{smallmatrix}
\text{Conjugate} \\
\text{base}
\end{smallmatrix}}{\mathop{B\left( OH \right)_{4}^{-}}}\,+\underset{\begin{smallmatrix}
\text{Conjugate} \\
\text{acid}
\end{smallmatrix}}{\mathop{{{H}^{+}}}}\,\] Remember In the given options to the question, (A), (B) and (C) are correct as all of these sentences have more or less similar meaning but here (C) option is the most appropriate one as it gives complete explanation of the fact that how boric acid can be combined with an acid.