Classification of Elements and Periodicity in Properties MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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211.
Predict the formula of a compound formed by aluminium and sulphur.
A
$$A{l_2}{S_2}$$
B
$$A{l_3}{S_2}$$
C
$$A{l_2}{S_3}$$
D
$$AlS$$
Answer :
$$A{l_2}{S_3}$$
$$Al - 3{e^ - } \to A{l^{3 + }},S + 2{e^ - } \to {S^{2 - }}$$
The formula for its sulphide is $$A{l_2}{S_3}.$$
212.
The electronic configuration of an element is $$1{s^2},2{s^2}\,2{p^6},3{s^2}\,3{p^3}.$$ What is the atomic
number of the element, which is present just below the above element in the periodic table?
A
33
B
34
C
36
D
49
Answer :
33
The element which present just below the given element will have outermost electronic configuration as $$4{s^2}4{p^3},$$ so its full electronic configuration is $$1{s^2},2{s^2}\,2{p^6},3{s^2}\,3{p^6},4{s^2},$$ $$3{d^{10}},4{p^3}$$ and hence, its atomic number is 33.
213.
Following statements regarding the periodic trends of chemical reactivity of the alkali metals and the halogens are given. Which of these statements gives the correct picture?
A
Chemical reactivity increases with increase in atomic
number down the group in both the alkali metals and
halogens
B
In alkali metals the reactivity increases but in the
halogens it decreases with increase in atomic number
down the group
C
The reactivity decreases in the alkali metals but
increases in the halogens with increase in atomic
number down the group
D
In both the alkali metals and the halogens the chemical
reactivity decreases with increase in atomic number
down the group
Answer :
In alkali metals the reactivity increases but in the
halogens it decreases with increase in atomic number
down the group
The alkali metals are highly reactive because their first ionisation potential is very low and hence they have great tendency to loses electron to form unipositive
ion.
NOTE : On moving down group - $$I$$ from $$Li$$ to $$Cs$$ ionisation enthalpy decreases hence the reactivity increases. The halogens are most reactive elements due to their low bond dissociation energy, high electron affinity and high enthalpy of hydration of halide ion. However their reactivity decreases with increase in
atomic number.
214.
Which of the following statements regarding the variation of atomic radii in the periodic table is not true?
A
In a group, there is continuous increase in size with increase in atomic number.
B
In $$4f$$ - series, there is a continuous decrease in size with increase in atomic number.
C
The size of inert gases is larger than halogens.
D
In 3rd period, the size of atoms increases with increase in atomic number.
Answer :
In 3rd period, the size of atoms increases with increase in atomic number.
Size of atoms decreases with increase in atomic number in a period.
215.
Consider the isoelectronic species, $$N{a^{ + }},M{g^{2 + }},{F^ - }$$ and $${O^{2 - }}.$$ The correct order of increasing length of their radii is
For isoelectronic species, ionic radii decrease with
increase in nuclear charge ( i.e., no. of protons ). Thus, the cation
with greater $$+ve$$ charge will have a smaller radius and the anion with greater $$-ve$$ charge will have a larger radius. Thus, the correct order of increasing ionic radii is $$M{g^{2 + }} < N{a^ + } < {F^ - } < {O^{2 - }}.$$
216.
Which of the following oxides is amphoteric in character?
A
$$Sn{O_2}$$
B
$$Si{O_2}$$
C
$$C{O_2}$$
D
$$CaO$$
Answer :
$$Sn{O_2}$$
$$CaO$$ is basic as it form strong base $$Ca{\left( {OH} \right)_2}$$ on reation with water.
$$CaO + {H_2}O \to Ca{\left( {OH} \right)_2}$$
$$C{O_2}$$ is acidic as it dissolve in water forming unstable carbonic acid.
$${H_2}O + C{O_2} \to {H_2}C{O_3}$$
Silica $$\left( {Si{O_2}} \right)$$ is insoluble in water and acts as a very weak acid.
$$Sn{O_2}$$ is amphoteric as it reacts with both acid and base.
$$Sn{O_2} + 2{H_2}S{O_4} \to Sn{\left( {S{O_4}} \right)_2} + 2{H_2}O$$
$$Sn{O_2} + 2KOH \to {K_2}Sn{O_3} + {H_2}O$$
217.
Which of the following is not a periodic property for the elements?
A
Electronegativity
B
Atomic size
C
Occurrence in nature
D
Ionization energy
Answer :
Occurrence in nature
No explanation is given for this question. Let's discuss the answer together.
218.
Match the column I with column II and mark the appropriate choice.
Column I
Column II
a.
$$3d$$ -transition series
1.
$$Z$$ = 58 to $$Z$$ = 71
b.
Lanthanoid series
2.
$$Z$$ = 39 to $$Z$$ = 48
c.
Actinoid series
3.
$$Z$$ = 21 to $$Z$$ = 30
d.
$$4d$$ -transition series
4.
$$Z$$ = 90 to $$Z$$ = 103
A
a - 1, b - 2, c - 3, d - 4
B
a - 2, b - 3, c - 4, d - 1
C
a - 3, b - 1, c - 4, d - 2
D
a - 4, b - 3, c - 1, d - 2
Answer :
a - 3, b - 1, c - 4, d - 2
No explanation is given for this question. Let's discuss the answer together.
219.
The amount of energy when million atoms of iodine are completely converted into $${I^ - }$$ ions in the vapour state according to the equation, $${I_{\left( g \right)}} + {e^ - } \to I_{\left( g \right)}^ - $$ is $$4.9 \times {10^{ - 13}}\,J.$$ What would be the electron gain enthalpy of iodine in terms of $$kJ\,mo{l^{ - 1}}$$ and $$eV$$ per atom?
A
295, 3.06
B
- 295, - 3.06
C
439, 5.09
D
- 356, - 7.08
Answer :
- 295, - 3.06
The electron gain enthalpy of iodine is equal to the energy released when 1 mole of iodine atoms in vapour state is converted into $${I^ - }$$ ions
$$\eqalign{
& {\Delta _{eg}}H = \frac{{4.9 \times {{10}^{ - 13}} \times 6.023 \times {{10}^{23}}}}{{{{10}^6}}} \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 29.5 \times {10^4}\,J\,mo{l^{ - 1}} \cr
& \,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 295\,kJ\,mo{l^{ - 1}} \cr} $$
Thus, electron gain enthalpy of iodine $$ = - 295\,kJ\,mo{l^{ - 1}}$$
We know that 1 $$eV$$ per atom $$ = 96.49\,kJ\,mo{l^{ - 1}}$$
∴ Electron gain enthalpy of iodine in $$eV$$ per atom $$ = - \frac{{295}}{{96.49}} = - 3.06\,eV$$ per atom
220.
Which of the following groups contains metals, non-metals and metalloids?