S - Block Elements MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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71.
Which of the following is not a similarity of beryllium with aluminium?
A
It becomes passive when treated with conc. $$HN{O_3}.$$
B
It forms polymeric covalent hydrides.
C
Carbonate of $$Be$$ is extremely stable.
D
Salts of $$Be$$ do not impart colour to the flame.
Answer :
Carbonate of $$Be$$ is extremely stable.
No explanation is given for this question. Let's discuss the answer together.
72.
A metal salt solution forms a yellow precipitate with potassium chromate in acetic acid, a white precipitate with dilute sulphuric acid but does not give precipitate with sodium chloride or iodide. The white precipitate obtained when sodium carbonate is added to the metal salt solution will consist of
A
lead carbonate
B
basic lead carbonate
C
barium carbonate
D
strontium carbonate
Answer :
barium carbonate
$$Pb$$ and $$Ba$$ both give yellow $$ppt.$$ with $${K_2}Cr{O_4}$$ in acetic acid and white precipitate with $$dil.\,{H_2}S{O_4}.$$ But lead salts give precipitate with sodium chloride or iodide whereas barium does not. It means given salt is barium salts and with sodium carbonate it gives white precipitate of barium carbonate.
73.
When chlorine is passed over dry slaked lime at room temperature, the main reaction product is
A
$$Ca{\left( {Cl{O_2}} \right)_2}$$
B
$$CaC{l_2}$$
C
$$CaOC{l_2}$$
D
$$Ca{\left( {OCl} \right)_2}$$
Answer :
$$CaOC{l_2}$$
When chlorine gas is passed over dry slaked lime, it form bleaching powder i.e. $$CaOC{l_2}.$$
$$Ca{\left( {OH} \right)_2} + C{l_2} \to CaOC{l_2} + {H_2}O$$
74.
Which nitrate will decompose to give $$N{O_2}$$ on heating?
A
$$NaN{O_3}$$
B
$$KN{O_3}$$
C
$$RbN{O_3}$$
D
$$LiN{O_3}$$
Answer :
$$LiN{O_3}$$
Only $$LiN{O_3}$$ gives $$N{O_2}$$ on heating. All other nitrates give oxygen.
\[\begin{align}
& 4LiN{{O}_{3}}\xrightarrow{\Delta }2L{{i}_{2}}O+4N{{O}_{2}}+{{O}_{2}} \\
& 2NaN{{O}_{3}}\xrightarrow{\Delta }2NaN{{O}_{2}}+{{O}_{2}} \\
\end{align}\]
75.
Amphoteric hydroxides react with both alkalies and acids. Which of the following group 2 metal hydroxides is soluble in sodium hydroxide?
A
$$Be{\left( {OH} \right)_2}$$
B
$$Mg{\left( {OH} \right)_2}$$
C
$$Ca{\left( {OH} \right)_2}$$
D
$$Ba{\left( {OH} \right)_2}$$
Answer :
$$Be{\left( {OH} \right)_2}$$
Beryllium hydroxide, $$Be{\left( {OH} \right)_2}$$ is amphoteric in nature, as it reacts with acid and alkali both.
$$Be{\left( {OH} \right)_2} + 2HCl \to $$ $$BeC{l_2} + 2{H_2}O$$
$$Be{\left( {OH} \right)_2} + 2NaOH \to $$ $$N{a_2}Be{O_2} + 2{H_2}O$$
76.
When a crystal of caustic soda is exposed to air, a liquid layer is deposited because :
A
Crystal loses water
B
Crystal absorbs moisture and $$C{O_2}$$
C
Crystal melts
D
Crystal sublimes
Answer :
Crystal absorbs moisture and $$C{O_2}$$
It is hygroscopic and deliquescent. It absorbs moisture and $$C{O_2}$$ to form $$N{a_2}C{O_3}$$
$$2NaOH + C{O_2} \to N{a_2}C{O_3} + {H_2}O$$
77.
Which of the following metals is required as cofactor by all enzymes utilising $$ATP$$ in phosphate transfer?
A
$$K$$
B
$$Ca$$
C
$$Na$$
D
$$Mg$$
Answer :
$$Mg$$
No explanation is given for this question. Let's discuss the answer together.
78.
Which is incorrect statement ?
A
The heats of hydration of the dipositive alkaline earth metal decrease with an increase in their ionic size
B
$$NaN{O_3}$$ forms $$N{a_2}{O_2}$$ on heating
C
Hydration of alkali metal ion is less than that of $$IIA$$ group
D
Alkaline earth metal ions, because of their much larger charge to size ratio, exert a much stronger electrostatic attraction on the oxygen of water molecule surrounding them
Answer :
$$NaN{O_3}$$ forms $$N{a_2}{O_2}$$ on heating
79.
For a good quality cement, the ratio of silica $$\left( {Si{O_2}} \right)$$ to alumina $$\left( {A{l_2}{O_3}} \right)$$ should lie between
A
1.5 - 3
B
2 - 2.5
C
2.5 - 4
D
4 - 6
Answer :
2.5 - 4
$$\eqalign{
& {\text{Generally the ratio is kept as :}} \cr
& \frac{{\% \,{\text{Silica}}}}{{\% \,A{l_2}{O_3}}} = 2.5 - 4.0 \cr} $$
80.
The following compounds have been arranged in order of their increasing thermal stabilities. Identify the correct order.
$${K_2}C{O_3}\left( {\text{i}} \right)\,\,MgC{O_3}\left( {{\text{ii}}} \right)$$ $$CaC{O_3}\left( {{\text{iii}}} \right)\,\,BeC{O_3}\left( {{\text{iv}}} \right)$$
A
(i) < (ii) < (iii) < (iv)
B
(iv) < (ii) < (iii) < (i)
C
(iv) < (ii) < (i) < (iii)
D
(ii) < (iv) < (iii) < (i)
Answer :
(iv) < (ii) < (iii) < (i)
The increasing thermal stability is
$$\mathop {BeC{O_3}}\limits_{\left( {{\text{iv}}} \right)} < \mathop {MgC{O_3}}\limits_{\left( {{\text{ii}}} \right)} < \mathop {CaC{O_3}}\limits_{\left( {{\text{iii}}} \right)} < \mathop {{K_2}C{O_3}}\limits_{\left( {\text{i}} \right)} $$
NOTE : Increasing size of cation decreases its polarization ability towards carbonate, making the compound more stable.