Potassium oxide

Potassium oxide (K₂O) 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 K₂O.

Production

Potassium oxide is produced from the reaction of oxygen and potassium; this reaction affords potassium oxide, K₂O. Treatment of the peroxide with potassium produces the oxide:

Alternatively and more conveniently, K₂O is synthesized by heating potassium nitrate with metallic potassium:

Potassium hydroxide cannot be further dehydrated to the oxide but it can react with molten potassium to produce it, releasing hydrogen as a byproduct.

Properties and reactions

K₂O crystallises in the antifluorite structure. In this motif the positions of the anions and cations are reversed relative to their positions in CaF₂, with potassium ions coordinated to 4 oxide ions and oxide ions coordinated to 8 potassium. K₂O is a basic oxide and reacts with water violently to produce the caustic potassium hydroxide. It is deliquescent and will absorb water from the atmosphere, initiating this vigorous reaction.