P - Block Elements MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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491.
$${{C_{60}}}$$, an allotrope of carbon cantains:
A
$$12$$ hexagons and $$20$$ pentagons.
B
$$18$$ hexagons and $$14$$ pentagons.
C
$$16\,$$ hexagons and $$16\,$$ pentagons.
D
$$20$$ hexagons and $$12$$ pentagons.
Answer :
$$20$$ hexagons and $$12$$ pentagons.
Fullerene $$\left( {{C_{60}}} \right)$$ contains $$20$$ hexagons ( six membered ) rings and 12 pentagons ( five membered rings ) .
492.
Which of the following is the most basic oxide?
A
$$A{l_2}{O_3}$$
B
$$S{b_2}{O_3}$$
C
$$B{i_2}{O_3}$$
D
$$Se{O_2}$$
Answer :
$$B{i_2}{O_3}$$
In $$A{l_2}{O_3},S{b_2}{O_3},B{i_2}{O_3}$$ and $$Se{O_2},B{i_2}{O_3}$$ is most basic oxide. As across the period basic nature of oxide decreases and on moving down the group it increases.
$$B{i_2}{O_3} + 6HCl \to 2BiC{l_3} + 3{H_2}O$$
493.
Which property of $$C{O_2}$$ makes it of biological and geochemical importance?
A
Its acidic nature
B
Its colourless and odourless nature
C
Its low solubility in water
D
Its high compressibility
Answer :
Its low solubility in water
Its low solubility in water makes it of biological and geo-chemical importance. It forms carbonic acid with water which dissociates to give $$HCO_3^ - $$ ions. $${H_2}C{O_3}/HCO_3^ - $$ buffer system helps to maintain $$pH$$ of blood between 7.26 - 7.42.
494.
Which of the following statements is false?
A
Radon is obtained from the decay of radium
B
Helium is inert gas
C
Xenon is the most reactive among the rare gases
D
The most abundant rare gas found in the atmosphere is helium
Answer :
The most abundant rare gas found in the atmosphere is helium
The amount of noble gases present in atmosphere ( in percent by ) is given below :
Element
Abundance (volume%)
$$He$$
$$524 \times {10^{ - 4}}$$
$$Ne$$
$$1.82 \times {10^{ - 3}}$$
$$Ar$$
$$0.934$$
$$Kr$$
$$1.14 \times {10^{ - 3}}$$
$$Xe$$
$$8.7 \times {10^{ - 6}}$$
So, argon is most abundant, not helium.
495.
When $$Pb{O_2}\,$$ reacts with conc. $$HN{O_3}$$ the gas evolved is
A
$$N{O_2}$$
B
$${O_2}$$
C
$${N_2}$$
D
$${N_2}O$$
Answer :
$${O_2}$$
$$Pb{O_2}$$ is a powerful oxidizing agent and liberate $$\,{O_2}$$ when
treated with acids.
$$2Pb{O_2} + 4HN{O_3} \to 2Pb{\left( {N{O_3}} \right)_2} + 2{H_2}O + {O_2} \uparrow $$
496.
A gas $$(X)$$ is obtained when copper reacts with dilute $$HN{O_3}.$$ The gas thus formed reacts with oxygen to give brown fumes of $$\left( Y \right).$$ $$\left( Y \right)$$ when dissolved in water gives an important acid $$(Z)$$ and the gas $$(X).$$ $$X, Y$$ and $$Z$$ respectively are
A
$$NO;N{O_2};HN{O_3}$$
B
$$N{O_2};NO;HN{O_3}$$
C
$${N_2}O;NO;HN{O_2}$$
D
$$NO;{N_2}O;HN{O_3}$$
Answer :
$$NO;N{O_2};HN{O_3}$$
$$3Cu + 8HN{O_{3\left( {dil} \right).}} \to 3Cu{\left( {N{O_3}} \right)_2}$$ $$ + \mathop {2NO}\limits_{\left( X \right)} + 4{H_2}O$$
$$\eqalign{
& 2NO + {O_2} \rightleftharpoons \mathop {2N{O_2}}\limits_{\left( Y \right)} \cr
& \mathop {3N{O_2}}\limits_{\left( Y \right)} + {H_2}O \to \mathop {2HN{O_3}}\limits_{\left( Z \right)} + \mathop {NO}\limits_{\left( X \right)} \cr} $$
497.
Which of the following statements is correct for $$CsB{r_3}$$ ?
A
Itisa covalent compound.
B
It contains $$C{s^{3 + }}$$ and $$B{r^ - }$$ ions.
C
Itcontains $$C{s^ + }$$ and $$Br_3^ - $$ lons
D
Itcontains $$C{s^ + }$$ and $$B{r^ - }$$ and lattice $$B{r_2}$$ molecule
$$\,CsB{r_3}$$ may be represented as $$C{s^ + }Br_3^ - $$
498.
Regarding $${F^ - }$$ and $$C{l^ - }$$ which of the following statement $$(s)$$ is/are correct?
$$\left( {\text{i}} \right)C{l^ - }$$ can give up an electron more easily than $${F^ - }.$$
$$\left( {{\text{ii}}} \right)C{l^ - }$$ is a better reducing agent than $${F^ - }.$$
$$\left( {{\text{iii}}} \right)C{l^ - }$$ is smaller in size than $${F^ - }.$$
$$\left( {{\text{iv}}} \right){F^ - }$$ can be oxidised more readily than $$C{l^ - }.$$
A
(i) and (ii)
B
(i), (ii) and (iv)
C
(iii) and (iv)
D
Only (i)
Answer :
Only (i)
The electronegativity of $${F^ - }$$ $$ion$$ is high, so it accept an electron and $$C{l^ - }$$ $$ion$$ can give an electron more easily. Also the size of $${F^ - }$$ is smaller than chloride ion $$\left( {C{l^ - }} \right).$$
499.
Which one of the following is correct pair with respect to molecular formula of xenon compound and hybridization state of xenon in it ?
A
$$Xe{F_4},s{p^3}$$
B
$$Xe{F_2},sp$$
C
$$Xe{F_2},s{p^3}d$$
D
$$Xe{F_4},S{p^2}$$
Answer :
$$Xe{F_2},s{p^3}d$$
Hybridisation in each case is $$Xe{F_4},s{p^3}{d^2},Xe{F_2},s{p^3}d.$$
500.
Oleum is
A
castor oil
B
oil of vitriol
C
fuming $${H_2}S{O_4}$$
D
None of these
Answer :
fuming $${H_2}S{O_4}$$
Disulphuric acid $$\left( {{H_2}{S_2}{O_7}} \right)$$ is called oleum or fuming sulphuric acid. It is strongest oxidising agent and more powerful dehydrating agent.