In which of the following reactions, hydrogen is evolved?
$I$. Reaction of sodium borohydride with iodine
$II$. Oxidation of diborane
$III$. Reaction of boron trifluoride with sodium hydride
$IV$. Hydrolysis of diborane

Dehydration of oxalic acid with concentrated $H_2SO_4$ produces ............

The maximum sum of the number of neutrons and protons in an isotope of hydrogen is

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.

Write the physical properties of $H_2$.

How do ortho and para hydrogen differ from each other?