Hydrogen is produced by the reaction:

Among the following,the correct statements are:
$I$. $LiH, BeH_2$ and $MgH_2$ are saline hydrides with significant covalent character.
$II$. Saline hydrides are volatile.
$III$. Electron-precise hydrides are Lewis bases.
$IV$. The formula for chromium hydride is $CrH$.
The correct option is:

Which type of ions are present in the anhydrous mixture of $KF$ and $HF$?

$NaH$ is an example of:

Asthma patients use a mixture of ........... for breathing.

What is $X$ in the following reaction?
$CO + 2 H_2 \xrightarrow{X} CH_3 OH$