Question

Which is the correct thermal stability order
for $H_{2}E$ $(E=O,S,Se,TeandPo$)?

• A. $H_{2}S$<$H_{2}O$<$H_{2}Se$<$H_{2}Te$<$H_{2}Po$
• B. $H_{2}O$<$H_{2}S$<$H_{2}Se$<$H_{2}Te$<$H_{2}Po$
• C. $H_{2}Po$<$H_{2}Te$<$H_{2}Se$<$H_{2}S$<$H_{2}O$
• D. $H_{2}Se$<$H_{2}Te$<$H_{2}Po$<$H_{2}O$<$H_{2}S$

Answer 1

The correct option is C $H_{2}Po$<$H_{2}Te$<$H_{2}Se$<$H_{2}S$<$H_{2}O$

On going down the group, the thermal stability of $H_{2}E$ decreases due to the decrease in the H–E bond energy.
Thus, the order is:
$H_{2}Po$<$H_{2}Te$<$H_{2}Se$<$H_{2}S$<$H_{2}O$