Question

Arrange the following hydrides of Group-16 elements in the increasing order of their thermal stability:

${\mathrm{H}}_2\mathrm{O},{\mathrm{H}}_2\mathrm{S},{\mathrm{H}}_2\mathrm{Se},{\mathrm{H}}_2\mathrm{Te}$

Answer 1

Hydrides of Group-16

• All the elements of Group 16 form hydrides of the type ${\mathrm{H}}_2\mathrm{E}$.
• With the decrease in enthalpy for the dissociation of $\text{H–E}$ bond down the group, the thermal stability of hydrides also decreases down the group.
• Hence, the increasing order of their thermal stability:
• ${\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{S}<{\mathrm{H}}_2\mathrm{O}$