Which of the following has maximum solubility in water?

$A$ metal $M$ reacts with nitrogen gas to afford $M_3N$. $M_3N$ on heating at high temperature gives back $M$ and on reaction with water produces a gas $B$. Gas $B$ reacts with aqueous solution of $CuSO_4$ to form a deep blue compound. $M$ and $B$ respectively are

Which of the following is not a product,when $RbO_2$ reacts with $H_2O$?

Which of the following compounds is completely water soluble?

What happens if the concentration of $Na^{+}$ ions increases in the body?

The chloride of an element gives a neutral solution in water. To which group of the periodic table does this element belong?