\[\begin{align} & N{{a}_{2}}C{{O}_{3}}+2S{{O}_{2}}+{{H}_{2}}O\to \underset{\left( A \right)}{\mathop{2NaHS{{O}_{3}}}}\,+C{{O}_{2}} \\ & \underset{\left( A \right)}{\mathop{2NaHS{{O}_{3}}}}\,+N{{a}_{2}}C{{O}_{3}}\to \underset{\left( B \right)}{\mathop{2N{{a}_{2}}S{{O}_{3}}}}\,+{{H}_{2}}O+C{{O}_{2}} \\ & \underset{\left( B \right)}{\mathop{2N{{a}_{2}}S{{O}_{3}}}}\,+S\xrightarrow{\text{Heat}}\underset{\left( C \right)}{\mathop{2N{{a}_{2}}{{S}_{2}}{{O}_{3}}}}\, \\ & N{{a}_{2}}{{S}_{2}}{{O}_{3}}+AgN{{O}_{3}}\to \underset{\left( D \right)}{\mathop{A{{g}_{2}}S}}\,+{{H}_{2}}S{{O}_{4}} \\ \end{align}\]

In going from top to bottom in a group, the first ionization potential decreases, thus $$Be > Mg > Ca$$

$$L{i^ + }$$ has maximum degree of hydration due to smallest size in the group hence its salts are mostly hydrated.

$$Be{\left( {OH} \right)_2}$$  is insoluble in water and thus has lower value of $${K_{sp}}.$$

$$ \bullet \,\,C{a^{2 + }}\,ions$$   are very important factor in blood clotting.
$$ \bullet \,\,C{a^{2 + }}\,ions$$   are very important for maintaining the regular heart beating.
$$ \bullet\, \,M{g^{2 + }}\,ions$$   is present in the green parts of plants i.e., chlorophyll.
$$ \bullet \,\,M{g^{2 + }}$$  can form a complex with $$ATP.$$

No explanation is given for this question. Let's discuss the answer together.

Bleaching powder is prepared by passing chlorine gas over dry slaked lime $$Ca{\left( {OH} \right)_2}$$   by Hesenclaver method or by Bachmann method.
$$Ca{\left( {OH} \right)_2} + C{l_2} \to CaOC{l_2} + {H_2}O$$

$$Ca{\left( {OCl} \right)_2},$$   calcium hypochlorite is the active ingredient in bleaching powder which releases chlorine.

$$2Ca{\left( {OH} \right)_2} + 2C{l_2} \to CaC{l_2} + $$       $$\mathop {Ca{{\left( {OCl} \right)}_2} + 2{H_2}O}\limits_{{\text{Bleaching powder}}} $$

Thermal decomposition of $${\left( {N{H_4}} \right)_2}Be{F_4}$$   is the best method for preparation of $$Be{F_2}.$$