The synonym for water gas when used in the production of methanol is:

Which compound on electrolysis produces $H_2$ gas at both electrodes?

Which of the following reactions give $H_2$ as one of the products? (Reactions are not balanced)
$I) NaBH_4 + I_2 \longrightarrow$
$II) B_2H_6 + N(CH_3)_3 \longrightarrow$
$III) Al + NaOH + H_2O \longrightarrow$
$IV) BF_3 + NaH \longrightarrow$

The oxidation states shown by hydrogen are

Calcium imide on hydrolysis gives gas $(B)$ which on oxidation by bleaching powder gives gas $(C)$. Gas $(C)$ on reaction with magnesium gives compound $(D)$ which on hydrolysis gives again gas $(B)$. Identify $(B)$,$(C)$ and $(D)$.

Ortho- and para-hydrogens have