PROPERTIES OF DIHYDROGEN

9.4.1 Physical Properties

Dihydrogen is a colourless, odourless,

tasteless, combustible gas. It is lighter than

air and insoluble in water. Its other physical

properties alongwith those of deuterium are

given in Table 9.1.

9.4.2 Chemical Properties

The chemical behaviour of dihydrogen (and for

that matter any molecule) is determined, to a

large extent, by bond dissociation enthalpy.

The H–H bond dissociation enthalpy is the

highest for a single bond between two atoms

of any element. What inferences would you

draw from this fact ? It is because of this factor

that the dissociation of dihydrogen into its

atoms is only ~0.081% around 2000K which

increases to 95.5% at 5000K. Also, it is

relatively inert at room temperature due