AIEEE 2004 (Chemistry) Mock Test

Which one of the following sets of ions represents a collection of isoelectronic species?

Among ${\text{Al}}_2{\text{O}}_3,{\text{SiO}}_2,{\text{P}}_2{\text{O}}_3$ and ${\text{SO}}_2$ the correct order of acid strength is:

The bond order in $\text{NO}$ is $2.5$ while that in ${\text{NO}}^{+}$ is $3$. Which of the following statements is true for these two species?

The formation of the oxide ion ${\text{O}}^{2-}(g)$ requires first an exothermic and then an endothermic step as shown below:
$\text{O}(g)+e^{-}\to {\text{O}}^{-}(g);\Delta H^{\circ }=-142{\text{kJ mol}}^{-1}$
${\text{O}}^{-}(g)+e^{-}\to {\text{O}}^{2-}(g);\Delta H^{\circ }=844{\text{kJ mol}}^{-1}$
The second step is endothermic because:

The states of hybridization of boron and oxygen atoms in boric acid (${\text{H}}_3{\text{BO}}_3$) are respectively: