Q. What is the best description of the change that occurs when $Na_{2}O(s)$ is dissolved in water?
A) Oxidation number of sodium decreases
B) Oxide ion accepts sharing in a pair of electrons
C) Oxide ion donates a pair of electrons
D) Oxidation number of oxygen increases
Explanation
(c)
$Na_{2}O + H_{2}O \rightarrow 2NaOH$
$\uparrow \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \uparrow$
Oxidation number of Na +1 +1
Oxygen -2 -2 -2
No change in oxidation number, so (a) and (d) are not true.
(b) is also not true.
[image:7_image11.emf]
Oxide ion donates a pair of electrons, thus changes to $OH^{-}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.