An ore of potassium is

The metal which gives hydrogen on treatment with acid as well as sodium hydroxide is

Molten sodium is used in nuclear reactors to

Nelson cell is used for the preparation of

Which alkali metals are useful as electrodes in photoelectric cells?

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 ......