Question

An ionic compound of potassium and oxygen has the empirical formula KO. Would you expect this compound to be potassium (II) oxide or potassium peroxide? Explain.

Short answer

The compound is potassium peroxide.

Step-by-step solution

Step 1:(Discussing about the nature of ions formed by oxygen)

Since potassium forms only one ion,$K^{+}$ ,no Roman numeral is used. Oxygen forms two ions; the oxide ion$O^{2-}$ and the peroxide ion${O_2}^{2-}$ .

Step 2:(Discussing about the nature of bond formed by potassium with the ions of oxygen)

The formula units of nearly all ionic compounds are also the empirical formulas, as they represent the lowest whole-number ratios of the ions in the compound, though there are exceptions. KO is one of those exceptions. The formula unit for potassium oxide is $K_{2}O$,which is also the empirical formula. The formula unit for potassium peroxide is role="math" localid="1663748192280" $K_2{O}_2$. The ratio of ions to ions is 1:1, so KO is the empirical formula for potassium peroxide. The reason that the formula unit for potassium peroxide is not reduced to KO, is that the peroxide ion has the formula ${O_2}^{2-}$. It is composed of two covalently bonded oxygen atoms plus two extra electrons. Therefore, the peroxide ion cannot be further reduced.