Question

Which of the following is preferentially formed on reaction of oxygen and potassium?
A) ${K_2}{O_2}$
B) $K{O_2}$
C) ${K_2}O$
D) ${K_2}{O_3}$

Answer 1

Potassium $K$ is an alkali metal as well as an essential mineral. It is a member of group 1 of periodic table. The common oxidation state of potassium is 1 and its atomic number is 19. While oxygen ${O_2}$ is a gas and member of chalcogen that is group 16 and it is having atomic number 8.

Complete answer:
Potassium $K$ reacts with oxygen vigorously when potassium metal is heated. It even reacts with oxygen when potassium metal is cut open, a layer of potassium oxide is formed.
Due to the large size of Potassium ($K$) atom, it preferentially accommodates and forms the bonds with two small oxygen (${O_2}$ ) atoms to give $K{O_2}$ . Hence, $K{O_2}$ is the preferential product when potassium reacts with water.
$4K + {O_2} \to {K_2}O$
Remember Potassium oxide is produced from the reaction of oxygen and potassium; this reaction affords potassium peroxide, ${K_2}{O_2}$ . Treatment of the peroxide with potassium produces the oxide:
${K_2}{O_2}$ + 2$K$ → 2 ${K_2}O$
Some of the common points are that the Burning $K$ in excess ${O_2}$​ gives the superoxide $K{O_2}$ ​.Reaction with a large excess of metal will form the Oxide ${K_2}O$ . The superoxide reacts with water to form the peroxide, ​ ${K_2}{O_2}$ at low Temperature and the oxide at higher Temperature both with liberation of${O_2}$ . Also ${K_2}O$ is more stable than $K{O_2}$ ​.

Hence option C is correct.

Note: Potassium oxide (${K_2}O$) is an ionic compound of potassium and oxygen. This pale yellow solid, the simplest oxide of potassium, is a rarely encountered, highly reactive compound. Some materials of commerce, such as fertilizers and cements, are assayed assuming the percent composition that would be equivalent to the chemical compound mixture ${K_2}O$ .