The pair$(s)$ of reagents that yield paramagnetic species is/are:
$A$. $Na$ and excess of $NH_3$
$B$. $K$ and excess of $O_2$
$C$. $Cu$ and dilute $HNO_3$
$D$. $O_2$ and $2-ethylanthraquinol$

Compare the solubility and thermal stability of the following compounds of the alkali metals with those of the alkaline earth metals.
$(a)$ Nitrates $(b)$ Carbonates $(c)$ Sulphates.

$A$ metal $M$ and its compound can give the following observable changes in a sequence of reactions: $M$ $\xrightarrow{\text{dilute } HNO_3} \text{Colourless solution}$ $\xrightarrow{\text{aqueous } NaOH} \text{White precipitate}$ $\xrightarrow{\text{excess } NaOH_{(aq)}} \text{Colourless solution}$ $\xrightarrow{H_2S} \text{White precipitate}$. Identify the metal $M$.

$A$ mixture of sodium oxide and calcium oxide is dissolved in water and saturated with excess carbon dioxide gas. The resulting solution is ...... It contains ......... :

Which of the following compounds is/are used for oxygenating the submarine or spaceshuttle?

Which orders are correct?
$(I)$ Thermal stability: $BeSO_4 < MgSO_4 < CaSO_4 < SrSO_4$
$(II)$ Basic nature: $CaO > MgO > BeO > ZnO$
$(III)$ Solubility in water: $LiOH < NaOH < KOH < RbOH$
$(IV)$ Melting point: $NaCl > KCl > RbCl > CsCl > LiCl$