$NaNO_3$ on heating gives which gas?

State the reasons for the following:
$(a)$ Why is a solution of $Na_{2}CO_{3}$ alkaline?
$(b)$ Why are alkali metals prepared by the electrolysis of their fused chlorides?
$(c)$ Why is sodium found to be more useful than potassium in biological systems?

Molten sodium is used in nuclear reactors to

The alkali metals form salt-like hydrides by direct synthesis at elevated temperatures. The thermal stability of these hydrides decreases in which of the following orders?

What is caused by an excess of $Na^+$ in the human body?

The oxide of potassium that does not exist is