Potassium nitrate is called

On heating,$LiNO_3$ gives how many compounds among the following?
$Li_2O, N_2, O_2, LiNO_2, NO_2$

Assertion $(A)$: Alkali metals are soft and have low melting and boiling points.
Reason $(R)$: This is because interatomic bonds are weak.

Fill in the blanks:
$(1)$ Sodium hydroxide is also known as ......
$(2)$ The reaction of sodium amalgam with water produces ...... and ...... gas.
$(3)$ Sodium hydroxide on reaction with $CO_2$ produces ......
$(4)$ Sodium hydrogen carbonate is known as ......

Explain the chemical properties of alkali metal elements (Group $I$).

What is the chemical formula of Chile saltpeter?