Identify the correct statements from the following. (i) Oxygen shows $-2,-1,+1$ and +2 oxidation states.…
Identify the correct statements from the following.
(i) Oxygen shows $-2,-1,+1$ and +2 oxidation states.
(ii) The thermal stability of $\mathrm{H}_2 \mathrm{O}, \mathrm{H}_2 \mathrm{Se}$ and $\mathrm{H}_2 \mathrm{~S}$ follows the order $\mathrm{H}_2 \mathrm{O} < \mathrm{H}_2 \mathrm{~S} < \mathrm{H}_2$ Se.
(iii) The reducing nature of $\mathrm{H}_2 \mathrm{Se}, \mathrm{H}_2 \mathrm{~S}$ and $\mathrm{H}_2 \mathrm{Te}$ follows the order $\mathrm{H}_2 \mathrm{~S} < \mathrm{H}_2 \mathrm{Se} < \mathrm{H}_2 \mathrm{Te}$
i, ii, iii
i, ii
i, iii
ii, iii
Solution
Oxygen shows $-2,-1,+1$ and +2 oxidation states.
(i) Oxygen shows -2 oxidation states in most of its compound while it shows ( - 1) O.S. in peroxides (like $\mathrm{H}_2 \mathrm{O}_2$ ), +1 in $\mathrm{O}_2 \mathrm{~F}_2$ and +2 in $\mathrm{OF}_2$.
Thus, it show $-2,-1,+1$ and +2 oxidation states.
(ii) The thermal stability of $\mathrm{H}_2 \mathrm{O}, \mathrm{H}_2 \mathrm{Se}$ and $\mathrm{H}_2 \mathrm{~S}$ follows the order $\mathrm{H}_2 \mathrm{O}>\mathrm{H}_2 \mathrm{~S}>\mathrm{H}_2 \mathrm{Se}$ This is because, on going down the group, the size of the central atom increases and therefore, its tendency to form stable covalent bond with hydrogen decreases. As a result, the $M-\mathrm{H}$ bond strength decreases and therefore, thermal stability decreases.
iii) The reducing nature of $\mathrm{H}_2 \mathrm{Se}, \mathrm{H}_2 \mathrm{~S}$ and $\mathrm{H}_2$ Te follows the order
$$
\mathrm{H}_2 \mathrm{~S} < \mathrm{H}_2 \mathrm{Se} < \mathrm{H}_2 \mathrm{Te}
$$
This is due to the decrease in thermal stability of the hydride greater the unstability of hydrides, the greater is its reducing character.
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