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 ionic compound with the empirical formula KO is most likely potassium peroxide, as the oxidation number of oxygen in this compound is -1. The given empirical formula can be considered as a reduced form of the chemical formula for potassium peroxide (K2O2/2), which maintains a neutral charge and is consistent with the 1:1 ratio of potassium and oxygen ions in the compound.

Step-by-step solution

Identify the oxidation number of potassium

Potassium belongs to the alkali metal group in the periodic table, and it has a +1 oxidation number. It is determined by the number of valence electrons it can lose to form a stable ion. In this case, potassium always loses one valence electron to achieve a stable electronic configuration.

Identify the oxidation number of oxygen

In a stable ion, oxygen usually has an oxidation number of -2. This indicates that oxygen typically gains two electrons to achieve a stable electronic configuration. However, there are certain compounds where oxygen exhibits different oxidation numbers, like peroxides in which oxygen has an oxidation number of -1.

Write the chemical formula for potassium(II) oxide

Potassium(II) oxide, also known as potassium oxide, has the chemical formula K2O. It consists of two potassium ions (each with a +1 oxidation number) and one oxygen ion (with a -2 oxidation number). The total charge of the compound is neutral because the sum of positive charges equals the sum of negative charges: 2(+1) + 1(-2) = 0.

Write the chemical formula for potassium peroxide

Potassium peroxide has the chemical formula K2O2. It consists of two potassium ions (each with a +1 oxidation number) and two oxygen ions (each with a -1 oxidation number, as it is in a peroxide). The total charge of the compound is also neutral: 2(+1) + 2(-1) = 0.

Compare the empirical formula with the chemical formulas of potassium(II) oxide and potassium peroxide

The given empirical formula is KO, which indicates that there is one potassium ion (with a +1 oxidation number) and one oxygen ion. Since there is no information about the oxidation state of oxygen, we can assume its most common oxidation state, -2. KO can be written as K2O2/2, which is a reduced form of the chemical formula for potassium peroxide, K2O2. Therefore, we can conclude that the compound is most likely potassium peroxide. In conclusion, the ionic compound with the empirical formula KO is most likely potassium peroxide. This is because the oxidation number of oxygen in this compound is -1, which agrees with the given empirical formula when it is written in a 1:1 ratio between potassium and oxygen ions.