Which of the following is a property of alkali metals?

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 ......

In the Solvay ammonia process,why does sodium bicarbonate precipitate?

Which metal gives $NH_4NO_3$ when it reacts with very dilute $HNO_3$ acid?

In Solvay process,$NH_3$ is recovered when the solution containing $NH_4Cl$ is treated with compound ' $X$ '. What is ' $X$ ' ?

Identify the element having general electronic configuration $ns^1$ from the following.