P - Block Elements MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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411.
Which of the following statements is/are true?
(i) Sulphur exhibits 6 coordination number in its compound.
(ii) Bond energy of $${F_2}$$ is less than $$C{l_2}.$$
(iii) $$PC{l_5}$$ does not exist but $$NC{l_5}$$ exists.
(iv) Elements of 15th group show only +3 and +5 oxidation states.
A
(i) and (ii)
B
(ii) only
C
(ii) and (iii)
D
All of these
Answer :
(i) and (ii)
Fluorine is more reactive than chlorine. So, bond energy of chlorine is greater than fluorine. Sulphur exhibits 6 coordination number. $$PC{l_5}$$ exists but $$NC{l_5}$$ does not exist as $$N$$ cannot expand its octet due to non-availability of $$d$$ - orbitals. The common oxidation states of group 15 elements are -3, +3 and 5.
412.
Correct order of $$O - O$$ bond length (increasing) in $${O_2},{H_2}{O_2}$$ and $${O_3}$$ is
No explanation is given for this question. Let's discuss the answer together.
414.
Mark the example which is not correct.
A
Non-combustible heavy liquid used as fire extinguisher - $$CC{l_4}$$
B
Blocks used to shield radioactive materials - Lead
C
Element which has property of leaving mark on paper - Graphite
D
A gas in solid form used as a refrigerant - Carbon monoxide
Answer :
A gas in solid form used as a refrigerant - Carbon monoxide
Solid $$C{O_2}$$ is used as refrigerant.
415.
Acidity of diprotic acids in aqueous solutions increases in the order
A
$${H_2}S < {H_2}Se < {H_2}Te$$
B
$${H_2}Se < {H_2}S < {H_2}Te$$
C
$${H_2}Te < {H_2}S < {H_2}Se$$
D
$${H_2}Se < {H_2}Te < {H_2}S$$
Answer :
$${H_2}S < {H_2}Se < {H_2}Te$$
Acidic strength of hydrides increases as the size of central atom increases which weakens the $$M—H$$ bond. Since, the size increases from $$S$$ to $$Te$$ thus acidic strength follows the order.
$${H_2}S < {H_2}Se < {H_2}Te$$
$${\text{Acidic}}\,{\text{nature}} \propto \frac{1}{{{\text{Bond}}\,{\text{dissociation}}\,{\text{enthalpy}}}}$$
$$S$$ to $$Te$$ size increases, bond dissociation enthalpy decreases and acidic nature increases.
416.
The structural formula of hypophosphorous acid is
A
B
C
D
Answer :
Hypophosphorous acid $$\left( {{H_3}P{O_2}} \right)$$ is monobasic acid, so its structure is
417.
Which of these is not a monomer for a high molecular mass silicon polymer?
A
$$MeSiC{l_3}$$
B
$$M{e_2}SiC{l_2}$$
C
$$M{e_3}SiCl$$
D
$$PhSiC{l_3}$$
Answer :
$$M{e_3}SiCl$$
$$M{e_3}SiCl$$ is not a monomer for a high molecular mass silicon polymer because it generates $$M{e_3}SiOH$$ when subjected to hydrolysis which contains only one reacting site. Hence, the polymerisation reaction stops just after first step.
418.
The acid which has a peroxy linkage is
A
sulphurous acid
B
pyrosulphuric acid
C
dithionic acid
D
Caro’s acid
Answer :
Caro’s acid
Peroxomonosulphuric acid, $${H_2}S{O_5}$$ is also known as Caro’s acid. It has peroxy linkage $$—O—O—$$ which is confirmed by $$X
$$ - ray studies.
419.
Which one of the following arrangements does not give the correct picture of the trends indicated against it?
A
$${F_2} > C{l_2} > B{r_2} > {I_2}$$ Oxidising power
B
$${F_2} > C{l_2} > B{r_2} > {I_2}$$ Electron gain enthapy
C
$${F_2} > C{l_2} > B{r_2} > {I_2}$$ Bond dissociation energy
D
$${F_2} > C{l_2} > B{r_2} > {I_2}$$ Electronegativity
Answer :
$${F_2} > C{l_2} > B{r_2} > {I_2}$$ Bond dissociation energy
Generally as the size of the atom increases, bond dissociation energy decreases, so in halogens $${I_2}$$ have lowest bond dissociation energy, but the bond dissociation energy of chlorine is higher than
that of fluorine because in fluorine there is a greater repulsion between non-bonding electrons $$(2p).$$
Hence, the order of bond dissociation energy is
$$\eqalign{
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{l_2} > {F_2}\, > B{r_2}\,\, > \,{I_2} \cr
& {\text{Bond}}\,\,{\text{dissociation}}\,\,\,\,\,243\,\,\,\,\,\,\,159\,\,\,\,\,\,\,\,193\,\,\,\,\,\,\,\,\,151 \cr
& {\text{energy (kJ/mol)}} \cr} $$
420.
$$C{O_2}$$ and $${N_2}$$ are non-supporters of combustion. However for putting out fires $$C{O_2}$$ is preferred over $${N_2}$$ because $$C{O_2}$$
A
does not burn
B
forms non-combustible products with burning substances
C
is denser than nitrogen
D
is a more reactive gas
Answer :
is denser than nitrogen
$$C{O_2}$$ being more dense covers the igniting material more effectively than $${N_2}.$$