Question

The thermal stability of hydrides of the Oxygen family is in order:

• A. ${\mathrm{H}}_2\mathrm{O}<{\mathrm{H}}_2\mathrm{S}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Po}$
• B. ${\mathrm{H}}_2\mathrm{S}<{\mathrm{H}}_2\mathrm{O}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Po}$
• C. ${\mathrm{H}}_2\mathrm{Po}<{\mathrm{H}}_2\mathrm{O}<{\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{S}$
• D. ${\mathrm{H}}_2\mathrm{Po}<{\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{S}<{\mathrm{H}}_2\mathrm{O}$

Answer 1

The correct option is D

${\mathrm{H}}_2\mathrm{Po}<{\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{S}<{\mathrm{H}}_2\mathrm{O}$

Explanation for correct option:

(D) ${\mathrm{H}}_2\mathrm{Po}<{\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{S}<{\mathrm{H}}_2\mathrm{O}$

• Thermal stability is nothing but the stability of molecules to resist the action of heat.
• The given hydrides are from the oxygen family.
• The trend of thermal stability is that as we move down the group, the thermal stability of the hydrides will decrease.
• This is due to the decrease in $\mathrm{M}-\mathrm{H}$ bond dissociation energy down the group with an increase in the size of the central atom.

So, ${\mathrm{H}}_2\mathrm{Po}<{\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{S}<{\mathrm{H}}_2\mathrm{O}$ this is the correct order.

Explanation for incorrect options:

The correct order for thermal stability of hydrides of the Oxygen family is ${\mathrm{H}}_2\mathrm{Po}<{\mathrm{H}}_2\mathrm{Te}<{\mathrm{H}}_2\mathrm{Se}<{\mathrm{H}}_2\mathrm{S}<{\mathrm{H}}_2\mathrm{O}$. Thus, options A, B, and C are incorrect.

Hence, the correct option is (D).