Which of the following ions forms a highly soluble hydroxide in water?

Match the following:

Compound	Uses
$1$. Soda ash	$a$. In purification of sugar
$2$. Calcium oxide	$b$. As an antacid
$3$. Baking soda	$c$. In paper and textile industries
	$d$. To prepare pure fats and oils

In the presence of air,washing soda loses $9$ molecules of water to form a monohydrate: $Na_2CO_3 \cdot 10H_2O \xrightarrow{\text{In open air}} Na_2CO_3 \cdot H_2O + 9H_2O$. This process is known as:

The reducing power of a metal depends on various factors. Suggest the factor which makes $Li$ metal the strongest reducing agent in aqueous solution.

State True or False:
$(1)$ Half-life of $^{223}Fr$ is $21 \ s$.
$(2)$ $Li^{+}$ has a high hydration enthalpy and therefore its salts are usually hydrated in nature.
$(3)$ Among all the alkali metals,only $Na$ can react with nitrogen of air and form a nitride.
$(4)$ Except $LiF$,other halides of $Li$ are soluble in water.

$KO_2$ finds use in oxygen cylinders used for space and submarines. The fact$(s)$ related to such use of $KO_2$ is/are: