Hydrogen is produced by the reaction:

Ortho- and para-hydrogens have

The ionization of a hydrogen atom gives rise to:

Consider the reactions:
$I$. $CO + 3 H_2 \xrightarrow{A} CH_4 + H_2 O$
$II$. $CO + 2 H_2 \xrightarrow{B} CH_3 OH$
$III$. $O_2 + 2 H_2 \xrightarrow{C} 2 H_2 O$
The catalysts $A, B, C$ are respectively:

The charring of sugar takes place when treated with concentrated $H_2SO_4$. What is the type of reaction involved in it?

What do you understand by the terms: $(i)$ hydrogen economy,$(ii)$ hydrogenation,$(iii)$ 'syngas',$(iv)$ water-gas shift reaction,and $(v)$ fuel-cell?