Liquid ammonia is used for refrigeration because

Asthma patients use a mixture of $.....$ for respiration.

Which one of the following substances is used in the laboratory for a fast drying of neutral gases?

The correct statements among $(a)$ to $(d)$ are:
$(a)$ Saline hydrides produce $H_2$ gas when reacted with $H_2O$.
$(b)$ Reaction of $LiAlH_4$ with $BF_3$ leads to $B_2H_6$.
$(c)$ $PH_3$ and $CH_4$ are electron-rich and electron-precise hydrides,respectively.
$(d)$ $HF$ and $CH_4$ are called as molecular hydrides.

Consider the following statements and identify which of them are correct:
$I.$ Atomic hydrogen is obtained by applying an electric arc to hydrogen gas.
$II.$ Hydrogen gas does not reduce heated aluminum.
$III.$ Finely divided palladium absorbs a large volume of hydrogen gas.
$IV.$ The reaction of $Na$ with $C_2H_5OH$ yields pure nascent hydrogen.

High purity $(>99.95\,\%)$ dihydrogen is obtained by: