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:

What is the correct order of ionic mobility for alkali metal ions in an aqueous medium?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R).$
Assertion $(A):$ Lithium salts are hydrated.
Reason $(R):$ Lithium has higher polarising power than other alkali metal group members.
In the light of the above statements,choose the most appropriate answer from the options given below:

Fill in the blanks:
$(1)$ $Li-Mg$ alloy is used to prepare ......
$(2)$ Colors of superoxides of alkali metals are ...... or ......
$(3)$ On combustion of lithium in the presence of air,it produces ...... and ......
$(4)$ On heating,lithium nitrate converts into ......

Give two uses of $NaCl$.

An element $A$ of group $1$ shows similarity to an element $B$ belonging to group $2$. If $A$ has maximum hydration enthalpy in group $1$,then $B$ is: