Nitrates of all the metals are

Heating a metal $X$ in nitrogen gas gives $Y$. The reaction of $Y$ with $H_2O$ produces a colorless gas. When this gas is passed through $CuSO_4$ solution,it produces a blue color. What is $Y$?

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

Magnesium liberates $H_2$ gas on reaction with

$KO_2$ finds use in oxygen cylinders used for space and submarines. The fact$(s)$ related to such use of $KO_2$ is/are:

The colour given to the flame by sodium salts is