When $MnO_2$ and $H_2SO_4$ are added to a salt $(A)$,the greenish yellow gas liberated indicates that salt $(A)$ is:

$SiO_2$ reacts with

At high temperature,nitrogen combines with $CaC_2$ to give:

Silicon is the main constituent of

When lead nitrate is heated,it gives

Reaction of an inorganic sulphite $X$ with dilute $H_{2}SO_{4}$ generates compound $Y$. Reaction of $Y$ with $NaOH$ gives $X$. Further,the reaction of $X$ with $Y$ and water affords compound $Z$. $Y$ and $Z$,respectively,are: