Question

Predict the product of water reacting with potassium oxide.
A) $\text{ }{{\text{H}}_{\text{2}}}\text{O +}{{\text{K}}_{\text{2}}}\text{O }\to \text{ 2KOH }$
B) $\text{ }{{\text{H}}_{\text{2}}}\text{O +}{{\text{K}}_{\text{2}}}\text{O }\to \text{ KOH }$
C) $\text{ }{{\text{H}}_{\text{2}}}\text{O +}{{\text{K}}_{\text{2}}}\text{O }\to \text{ 2KO}{{\text{H}}_{\text{2}}}$
D) $\text{ }{{\text{H}}_{\text{2}}}\text{O +}{{\text{K}}_{\text{2}}}\text{O }\to \text{ }{{\text{H}}_{\text{2 }}}\text{+ KOH }$

Answer 1

Potassium oxide $\text{ }{{\text{K}}_{\text{2}}}\text{O }$ is an ionic compound and readily dissolves in water. It is a basic oxide of potassium .oxides ions are unstable in an aqueous solution. The abstract the proton from the solvent and form hydroxide $\text{ O}{{\text{H}}^{-}}\text{ }$ ions. The reaction of conversion of oxide ions in the hydroxide ion is as shown below,
$\text{ }{{\text{O}}^{\text{2}-}}\text{ + }{{\text{H}}_{\text{2}}}\text{O }\to \text{ 2O}{{\text{H}}^{-}}\text{ }$

Complete step by step answer:
Potassium hydroxide $\text{ }{{\text{K}}_{\text{2}}}\text{O }$ is an inorganic compound. When Potassium oxide is added into the water undergoes a chemical reaction with water. In water, potassium oxide dissociates into its corresponding ions. Potassium exists as a potassium ion $\text{ }{{\text{K}}^{\text{+ }}}$ and oxygen as an oxide ion $\text{ }{{\text{O}}^{\text{2}-}}\text{ }$.
The reaction for the dissociation of potassium oxide is as shown below,
$\text{ }{{\text{K}}_{\text{2}}}\text{O(s) }\to \text{ }{{\text{K}}^{\text{+ }}}\text{(aq)+ }{{\text{O}}^{2-}}\text{ (aq)}$...............(1)
Here one oxide ions require two potassium ions to balance the charge. Oxide ion is a conjugate base of hydroxide in $\text{ O}{{\text{H}}^{-}}\text{ }$ .generally oxide ion is found to be unstable in the aqueous solutions. In an aqueous solution instead of existing as an oxide ion, it abstracts a proton from the solvent and converts itself from oxide to hydroxide. The reaction is as shown below,
$\text{ }{{\text{O}}^{\text{2}-}}\text{ + }{{\text{H}}_{\text{2}}}\text{O }\to \text{ 2O}{{\text{H}}^{-}}\text{ }$....................(2)
Thus in an aqueous solution, the potassium ion interacts with the hydroxide ion. Potassium ion has a $\text{ +1 }$ charge which is well balanced by the one hydroxide molecule having a $\text{ }-\text{1 }$ charge. Thus reaction between potassium ion and hydroxide ion is as shown below,
$\text{ }{{\text{K}}^{\text{+}}}\text{ + O}{{\text{H}}^{-}}\text{ }\to \text{ KOH }$................(3)
Now on combining equation (1), (2), and (3) we get a final equation as follows,
$\text{ }{{\text{K}}_{\text{2}}}\text{O + }{{\text{H}}_{\text{2}}}\text{O }\to \text{ 2KOH }$

Hence, (A) is the correct option.

Note: The flow of reaction depends on the stability of oxide ions. Oxide is stable in solid form. However it loses its stability in an aqueous solution. It is a basic oxide thus reacts vigorously with water to produce basic hydroxide. Oxide compounds are very reactive. Similar reactions can be written for calcium oxide .when calcium oxide reacts with water from basic calcium hydroxide. However, oxides of non-metal are acidic.