The water gas on reacting with cobalt as a catalyst forms

What are metallic or interstitial hydrides? How do they differ from molecular hydrides?

$H_2SO_4$ acts as a dehydrating agent in its reaction with:

Complete the following reactions:
$(i) \, H_{2(g)} + M_m O_{o(s)} \xrightarrow{\Delta }$
$(ii) \, CO_{(g)} + H_{2(g)} \xrightarrow[catalyst]{\Delta }$
$(iii) \, C_3 H_{8(g)} + 3 H_2 O_{(g)} \xrightarrow[catalyst]{\Delta }$
$(iv) \, Zn_{(s)} + NaOH_{(aq)} \xrightarrow{heat}$

In context with the industrial preparation of hydrogen from water gas $(CO + H_2)$,which of the following is the correct statement?

Metals of groups $7$,$8$,and $9$ do not form metallic hydrides. This is termed as