S - Block Elements MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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191.
Which is not correctly matched
(i) Basic strength $$C{s_2}O < R{b_2}O < {K_2}O < N{a_2}O < L{i_2}O$$ of oxides.
(ii) Stability of $$N{a_2}{O_2} < {K_2}{O_2} < R{b_2}{O_2} < C{s_2}{O_2}$$ peroxides.
(iii) Stability of $$LiHC{O_3} < NaHC{O_3} < KHC{O_3} < RbHC{O_3} < CsHC{O_3}.$$
(iv) Melting point $$NaF < NaCl < NaBr < NaI$$
A
(i) and (iv)
B
(i) and (iii)
C
(i) and (ii)
D
(ii) and (iii)
Answer :
(i) and (iv)
Basic strength of the oxides increases in the order $$L{i_2}O < N{a_2}O < {K_2}O < R{b_2}O < C{s_2}O.$$ The increase in basic strength is due to the decrease in $$I.E.$$ and increase in electropositive character.
The melting points of the halides decrease in the order $$NaF > NaCl > NaBr > NaBr > NaI,$$ as the size of the halide ion increases. The decrease in melting point is due to increase in the covalent character with increase in the size of anion according to Fajan's rule.
192.
Suspension of slaked lime in water is known as
A
lime water
B
quick lime
C
milk of lime
D
aqueous solution of slaked lime
Answer :
milk of lime
No explanation is given for this question. Let's discuss the answer together.
193.
Which of the following is arranged according to increasing basic strength?
A
$$CaO < MgO < SrO < BaO < BeO$$
B
$$BaO < SrO < CaO < MgO < BeO$$
C
$$BeO < MgO < CaO < BaO < SrO$$
D
$$BeO < MgO < CaO < SrO < BaO$$
Answer :
$$BeO < MgO < CaO < SrO < BaO$$
Basic strength of oxides increases down the group.
194.
Based on lattice energy and other considerations which one of the following alkali metal chlorides is expected to have the highest melting point?
A
$$RbCl$$
B
$$KCl$$
C
$$NaCl$$
D
$$LiCl$$
Answer :
$$NaCl$$
$$LiCl$$ has partly covalent character. Other halides are ionic in nature. Lattice energy decreases with increase of ionic radius of cation, anion being the same. Larger is the lattice energy, the higher will be m. pt. hence
$$NaCl$$ will have highest lattice energy.
195.
Which of the bicarbonates does not exist in solid state?
A
$$NaHC{O_3}$$
B
$$KHC{O_3}$$
C
$$Ca{\left( {HC{O_3}} \right)_2}$$
D
$$RbHC{O_3}$$
Answer :
$$Ca{\left( {HC{O_3}} \right)_2}$$
Calcium bicarbonate exists in the form of solution.
196.
Alkali metals react with water Vigorously to form hydroxides and dihydrogen. Which of the following alkali metals reacts with water least vigorously?
A
$$Li$$
B
$$Na$$
C
$$K$$
D
$$Cs$$
Answer :
$$Li$$
$$Li$$ reacts with water least vigorously due to small size and very high hydration energy.
197.
Superoxides of alkali metals act as oxidising agents while normal oxides are basic in nature. The oxide which is paramagnetic in nature due to presence of
unpaired electron is
A
$$N{a_2}{O_2}$$
B
$$K{O_2}$$
C
$$N{a_2}O$$
D
$${K_2}{O_2}$$
Answer :
$$K{O_2}$$
Superoxides are paramagnetic in nature due to presence of one unpaired electron in $${\pi ^ * }2p\,MO.$$
198.
The solubility of metal halides depends on their nature, lattice enthalpy and hydration enthalpy of the individual ions. Amongst fluorides of alkali metals, the lowest solubility of $$LiF$$ in water is due to
A
ionic nature of lithium fluoride
B
high lattice enthalpy
C
high hydration enthalpy for lithium ion
D
low ionisation enthalpy of lithium atom
Answer :
high lattice enthalpy
The low solubility of $$LiF$$ in water is due to its high
lattice enthalpy. Smaller $$L{i^ + }$$ ion is stabilised by smaller $${F^ - }$$ ion.
199.
Which of the following does not form an oxide on heating?
A
$$ZnC{O_3}$$
B
$$CaC{O_3}$$
C
$$L{i_2}C{O_3}$$
D
$$N{a_2}C{O_3}$$
Answer :
$$N{a_2}C{O_3}$$
$$N{a_2}C{O_3}$$ does not decompose to form $$N{a_2}O.$$
200.
Which of the following is not correct ?
A
\[2L{{i}_{2}}O\xrightarrow[673K]{\text{heat}}L{{i}_{2}}{{O}_{2}}+2Li\]
B
\[2{{K}_{2}}O\xrightarrow[673K]{\text{heat}}{{K}_{2}}{{O}_{2}}+2K\]
C
\[2N{{a}_{2}}O\xrightarrow[673K]{\text{heat}}N{{a}_{2}}{{O}_{2}}+2Na\]
D
\[2R{{b}_{2}}O\xrightarrow[673K]{\text{heat}}R{{b}_{2}}{{O}_{2}}+2Rb\]