241. Which of the following materials conducts electricity?
A
Crystalline potassium chloride
B
Fused sulphates
C
Molten sodium chloride
D
Diamond
Answer :
Molten sodium chloride
242. Which of the following is not true about $$s$$ - block elements?
A
They have large atomic sizes.
B
They have lower ionisation enthalpies.
C
They have variable oxidation state.
D
They form basic oxides.
Answer :
They have variable oxidation state.
243. The solubilities of carbonates decrease down the magnesium group due to a decrease in
A
hydration energies of cations
B
inter-ionic attraction
C
entropy of solution formation
D
lattice energies of solids
Answer :
hydration energies of cations
244. Sodium salt of an organic acid $$'X'\,$$ produces effervescences with conc. $${H_2}S{O_4}.\,$$ $$'X'\,$$ reacts with the acidified aqueous $$\,CaC{l_2}$$ solution to give a white precipitate which decolourises acidic solution of $$KMn{O_4}.$$ $$'X'\,$$ is :
A
$${C_6}{H_5}COONa$$
B
$$HCOONa$$
C
$$C{H_3}COONa$$
D
$$N{a_2}{C_2}{O_4}$$
Answer :
$$N{a_2}{C_2}{O_4}$$
.PNG "S - Block Elements mcq solution image")
245. Which of the following is not a use of baking soda?
A
In medicines as antacid.
B
As a component of baking powder.
C
In removing permanent hardness of water.
D
In fire extinguishers.
Answer :
In removing permanent hardness of water.
246. Nitrogen dioxide cannot be prepared by heating
A
$$KN{O_3}$$
B
$$Pb{\left( {N{O_3}} \right)_2}$$
C
$$Cu{\left( {N{O_3}} \right)_2}$$
D
$$AgN{O_3}$$
Answer :
$$KN{O_3}$$
247. $${E^ \circ }$$ for $$\frac{{C{l_2}}}{{C{l^ - }}} = + 1.36,\frac{{{I_2}}}{{{I^ - }}} = + 0.53,$$ $$\frac{{A{g^ + }}}{{Ag}} = + 0.79,\frac{{N{a^ + }}}{{Na}} = - 2.71$$ and $$\frac{{L{i^ + }}}{{Li}} = - 3.04\,V.$$ What is the order of decreasing reducing strength for these species?
A
$$Li > C{l^ - } > Ag > {I^ - } > Na$$
B
$$Li > Na > {I^ - } > Ag > C{l^ - }$$
C
$$C{l^ - } > Ag > {I^ - } > Na > Li$$
D
$$Na > Li > Ag > C{l^ - } > {I^ - }$$
Answer :
$$Li > Na > {I^ - } > Ag > C{l^ - }$$
248. The ionic mobility of alkali metal ions in aqueous solution is maximum for
A
$$L{i^+}$$
B
$$N{a^ + }$$
C
$${K^ + }$$
D
$$R{b^ + }$$
Answer :
$$R{b^ + }$$
249. The alkali metals are low melting. Which of the following alkali metals is expected to melt if the room temperature rises to $$30{\,^ \circ }C?$$
A
$$Na$$
B
$$K$$
C
$$Rb$$
D
$$Cs$$
Answer :
$$Cs$$
250. The formula for calcium chlorite is
A
$$Ca{\left( {Cl{O_4}} \right)_2}$$
B
$$Ca{\left( {Cl{O_3}} \right)_2}$$
C
$$CaCl{O_2}$$
D
$$Ca{\left( {Cl{O_2}} \right)_2}$$
Answer :
$$Ca{\left( {Cl{O_2}} \right)_2}$$