Potassium chlorate KClO3 decomposes thermally to form potassium chloride KCl and oxygen gas is given off. This is in the presence of a catalyst, manganese iv oxide.
Hence, what is being said in essence is that when potassium chloride is heated in the presence of manganese iv oxide catalyst, oxygen is given off as the gaseous product with the formation of potassium chloride.
The chemical equation for the reaction is :
2KClO3 ——-> 2KCl + 3O2
This procedure is one of most important ways through which oxygen can be produced in the laboratory and can be used as a source of oxygen is industrial processes if on a large scale