A metal X forms a water soluble salt XNO₃. When an aqueous solution of XNO₃ is added to common salt solution, then a white precipitate fo compound Y is formed along with sodium nitrate solution. Metal X is said to be the best conductor of electricity and it does not evolve hydrogen when put in dilute hydrohloric acid.

(a) What is metal X ?
(b) What is salt XNO₃ ?