Stability of ionic compounds decreases with decrease in lattice enthalpy. Thus stability of alkaline earth metal hydroxides decreases with decrease in lattice enthalpy as the size of alkali earth metal cations increases down the group.
83.
Which of the following does not show diagonal relationship between beryllium and aluminium?
A
Both $$BeO$$ and $$A{l_2}{O_3}$$ are amphoteric in nature.
B
Both beryllium and aluminium form polymeric covalent hydrides.
C
Both beryllium and aluminium form nitrides with nitrogen which evolve $$N{H_3}$$ with water.
The size of $$M{g^{2 + }}$$ is minimum among $$N{a^ + },C{a^{2 + }},{K^ + }$$ and $$M{g^{2 + }}$$ and size of $$C{l^ - }$$ is more than $${F^ - }.$$ so the ratio of size of cation and anion are minimum in $$MgC{l_2}.$$
85.
Which of the following increasing orders is not correct as per the property indicated against it?
A
$$CsCl < RbCl < KCl < NaCl$$ $$ < LiCl$$ ( Lattice energy )
B
$$LiOH < NaOH < KOH$$ ( Solubility in water )
C
$$L{i^ + } < N{a^ + } < {K^ + } < R{b^ + } < C{s^ + }$$ ( Size of hydrated ion )
Increasing size of hydrated ion is $$C{s^ + } < R{b^ + } < {K^ + } < N{a^ + } < L{i^ + }.$$
86.
Dehydration of hydrates of halides of calcium, barium and strontium i.e., $$CaC{l_2} \cdot 6{H_2}O,BaC{l_2} \cdot 2{H_2}O,$$ $$SrC{l_2} \cdot 6{H_2}O,$$ can be achieved by heating. These become wet on keeping in air. Which of the following statements is correct about these halides?
A
Act as dehydrating agent.
B
Can absorb moisture from air.
C
Tendency to form hydrate decreases from calcium to barium.
The crystal structures of $$NaHC{O_3}$$ and $$KHC{O_3}$$ both show hydrogen bonding but are different. In $$NaHC{O_3},$$ the $$HCO_3^ - \,ions$$ are linked into an infinite chain, while in $$KHC{O_3},$$ a dimeric anion is formed.
88.
The increasing order of basic character of oxides $$MgO,SrO,{K_2}O$$ and $$C{s_2}O$$ is
Basic character of oxides increases down the group while decreases in a period.
89.
\[ZnC{{l}_{2}}+NaHC{{O}_{3}}\xrightarrow{\text{Heat}}\left( A \right)\] \[\xrightarrow{\text{Heat}}\left( B \right)+\left( C \right){{H}_{2}}O\left( B \right)+NaOH\] \[\to \left( D \right)\]
Identify the compound $$(D)$$ present in the solution.
\[\begin{align}
& ZnC{{l}_{2}}+2NaHC{{O}_{3}}\xrightarrow{\Delta }\underset{\left( A \right)}{\mathop{Zn{{\left( HC{{O}_{3}} \right)}_{2}}}}\,+2NaCl \\
& \underset{\left( A \right)}{\mathop{Zn{{\left( HC{{O}_{3}} \right)}_{2}}}}\,\xrightarrow{\Delta }\underset{\left( B \right)}{\mathop{ZnC{{O}_{3}}}}\,+{{H}_{2}}O+\underset{\left( C \right)}{\mathop{C{{O}_{2}}}}\,\uparrow \\
& \underset{\left( B \right)}{\mathop{ZnC{{O}_{3}}}}\,+2NaOH\to \underset{\left( D \right)}{\mathop{N{{a}_{2}}Zn{{O}_{2}}}}\,+2{{H}_{2}}O \\
\end{align}\]
90.
A metal $$X$$ reacts with water to produce a highly combustible gas $$Y,$$ and a solution $$Z.$$ Another metal $$P$$ reacts with $$Z$$ to give the same gas $$Y.$$ $$X, Y, Z$$ and $$P$$ respectively are