P - Block Elements MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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161.
$${H_3}P{O_2}$$ is the molecular formula of an acid of phosphorous. Its name and basicity respectively are
A
phosphorous acid and 2
B
hypophosphorous acid and 2
C
hypophosphorous acid and one
D
hypophosphoric acid and two
Answer :
hypophosphorous acid and one
The name of $${H_3}P{O_2}$$ is hypophosphorous acid when dissolve in water, it gives only one $${H^ + },$$ so its basicity is one.
162.
The increasing order of atomic radii of the following Group 13 elements is
A
$$A\ell < Ga < In < T\ell $$
B
$$Ga < A\ell < In < T\ell $$
C
$$A\ell < In < Ga < T\ell $$
D
$$A\ell < Ga < T\ell < In$$
Answer :
$$Ga < A\ell < In < T\ell $$
Atomic radii increases on moving down a group. However due to poor shielding effect of $$d$$ orbit, atomic radius of $$Ga\,$$ is smaller than $$Al$$ (anomaly). Thus the correct order is $$Ga < A\ell < In < T\ell $$
163.
The factor responsible for weak acidic nature of $$B-F$$ bonds in $$B{F_3}$$ is
A
large electronegativity of fluorine
B
three centred two electron bonds in $$B{F_3}$$
C
$$p\pi {\text{ - }}d\pi $$ back bonding
D
$$p\pi {\text{ - }}p\pi $$ back bonding
Answer :
$$p\pi {\text{ - }}p\pi $$ back bonding
It is $$p\pi {\text{ - }}p\pi $$ back bonding involving $$B$$ and $$F.$$ The smaller atoms show more back bonding.
164.
Among the following, the correct order of acidity is
As the oxidation state of halogen i.e. $$-Cl$$ in this case increases, acidity of oxyacid increases.
$$HClO:$$ Oxidation state of $$Cl = + 1$$
$$HCl{O_2}:$$ Oxidation state of $$Cl = + 3$$
$$HCl{O_3}:$$ Oxidation state of $$Cl = + 5$$
$$HCl{O_4}:$$ Oxidation state of $$Cl = + 7$$
Therefore, the correct order of acidity would be
$$HClO < HCl{O_2} < HCl{O_3} < HCl{O_4}$$
165.
Electrolytic reduction of alumina to aluminium by Hall-Heroult process is carried out
A
in the presence of $$NaCl$$
B
in the presence of fluorite
C
in the presence of cryolite which forms a melt with lower melting temperature
D
in the presence of cryolite which forms a melt with higher melting temperature
Answer :
in the presence of cryolite which forms a melt with lower melting temperature
Cryolite reduces the melting temperature.
166.
Excessive release of $$C{O_2}$$ into the atmosphere results in:
A
global warming
B
polar vortex
C
formation of smog
D
depletion of ozone
Answer :
global warming
Global warming is caused by the emission of green house gases. $$72\% $$ of the totally emitted green house gases is $$C{O_2}$$. Therefore, excessive release of $$C{O_2}$$ is the main cause of global warming.
167.
Among $$K, Ca, Fe$$ and $$Zn,$$ the element which can form more than one binary compound with chlorine is
A
$$Fe$$
B
$$Zn$$
C
$$K$$
D
$$Ca$$
Answer :
$$Fe$$
A binary compound is that compound which is formed by two different elements. Metals or elements which shows variable oxidation states can form more than one binary compound. In the given elements only $$Fe$$ shows + 2 and + 3 oxidation states. So, it can form two binary compounds with chlorine as $$FeC{l_2}$$ and $$FeC{l_3}.$$
168.
Which of the following is correct representation of reaction of acidified permanganate solution with sulphur dioxide?
169.
The catenation tendency of $$C, Si$$ and $$Ge$$ is in the order $$Ge < Si < C.$$ The bond energies $$\left( {{\text{in}}\,kJ\,mo{l^{ - 1}}} \right)$$ of $$C - C,Si - Si$$ and $$Ge - Ge$$ bonds are respectively
A
348, 297, 260
B
297, 348, 260
C
348, 260, 297
D
260, 297, 348
Answer :
348, 297, 260
The linking of identical atoms with each other to form long chains is called catenation. However, this property decreases from carbon to lead. Decrease of this property is associated with $$M-M$$ bond energy which decreases from carbon to lead.
170.
Shapes of certain interhalogen compounds are stated below. Which one of them is not correctly stated ?
A
$$I{F_7}:$$ pentagonal bipyramidal
B
$$Br{F_5}:$$ trigonal bipyramidal
C
$$Br{F_3}:$$ planar $$T$$-shaped
D
$$IC{I_3}:$$ planar dimeric
Answer :
$$Br{F_5}:$$ trigonal bipyramidal
The molecular geometry of $$Br{F_5}$$ is square pyramidal with asymmetric charge distribution on the central atom.