What is the chemical formula of sodium sulfite?

Write true or false for the following statement:
Hydrogen gas is evolved when a metal reacts with nitric acid.

$A$ piece of $Zn$ metal cannot displace which of the following metal ions from its salt solution?

Why does a magnesium ribbon start floating when it is placed in hot water?

$(a)$ $A$ substance $X$,an oxide of a metal,is used extensively in the cement industry. This element is found in our bones also. On treatment with water,it forms a solution which turns red litmus blue. Identify $X$ and also write the chemical reaction involved.
$(b)$ Choose a metal from the following metals which reacts only with hot water: Sodium,magnesium,iron. Mention the products formed during the reaction.

Name a non-metal which is lustrous and a metal which is non-lustrous.