Since, the anion is common in all and its size being much larger compared to constant within a particular group. Only the hydration enthalpies derease down the group, which results decrease in the solubility in same direction.

2 Mg + CO_{2 \(\underrightarrow { \Delta } \)}   MgO + C

(i) Alkali and alkaline earth metals are themselves strong reducing agents. Therefore, these metals cannot be obtained by chemical reduction of their oxides and other compounds.
(ii) These metals are highly electropositive in nature.So these cannot be displaced from the aqueous solutions of their salts by other metals.

No, (NH₄)₂CO₃ reacts with NaCl as
(NH₄)₂CO₃ + 2NaCl \(\leftrightharpoons \) Na₂CO₃ + 2NH₄Cl
Because the products obtained Na₂CO₃ and NH₄Cl are highly soluble and the equilibrium will not shift in forward direction. That's why in the Solvay process, we cannot obtain sodium carbonate directly by treating the solution containing (NH₄)₂CO₃ with sodium chloride.

The stability of peroxide or superoxide increases as the size of metal ion increases i.e.
 KO₂  <  RbO₂  <  CsO₂
The reactivity of alkali metals toward oxygen to form different oxides is due to string positive field around each alkali metal cation. Li⁺ is the smallest. it does not allow O2^-  ion to react with O2 further. Na⁺ is larger than Li, its positive field is weaker than Li⁺.
It cannot prevent the conversion of O^2- into O₂^2-. The large ions such as K⁺, Rb⁺ and Cs⁺ permit  O₂^2- ion to react with O2 forming superoxide ion O^2-
\({ O }_{ 2 }^{ 2- }  \overset { \frac { 1 }{ 2 } { O }_{ 2 } }{ \longrightarrow  } O^{2-}   \overset { { O }_{ 2 } }{ \longrightarrow  } 2 { O }_{ 2 }^{ - }\)
Furthermore, increased stability of the peroxide or superoxide with increase in the size of metal ion is due to the stabilisation of large anions by larger cations through lattice energy effect.

Alkali metals have only one valence electron per metal atom. As a result, the binding energy of alkali metal ions in the close-packed metal lattices are weak. Therefore these are soft and have low melting points.

The electrode potential, i.e. reduction potential of Na (-2.71 V) or K (-2.92) is much lower than that of H₂ O
(-0.83 V), therefore, upon electrolysis, water gets reduced in preference to Na⁺ or K⁺ ions. In other words, sodium and potassium cannot be obtained by electrolytic reduction of Na⁺ and K⁺ ions in aqueous solution.

Aluminium alloys such as duralumin is light, tough and resistant to corrosion and hence, it is used in making aircraft body

s-block contains only two groups; group 1 (alkali metals) and group 2 (alkaline earth metals)

Na₂ O₂ (s)  + 2 H₂ O (l)  \(\longrightarrow \)  2 NaOH (aq) + H₂ O₂ (aq)

H₂ gas is evolved which catches fire due to the liberation of extreme heat in the reaction.
2 Na (s) + 2 H₂ O(l) \(\longrightarrow \)  2 NaOH (aq) + H₂ (g)

Because in presence of moisture and CO₂ (which is present in air ), Na₂O² is converted top NaOH and Na₂Co₃ respectively both which are white in colour .
Na₂O₂ + H₂O \(\rightarrow\) 2NaOH + H₂O₂
2Na₂O₂ + 2CO₂ \(\rightarrow\) 2Na₂CO₃ + O₂