what makes up sulfur trioxide
The Reaction of Oxygen with Sulfur Dioxide to make Sulfur Trioxide. Sulfur dioxide is made by reacting sulfur with oxygen. Sulfur dioxide can be made to react with more oxygen to make sulfur trioxide. This is another example of oxidation. The reaction is reversible (shown by the arrow). The forward reaction (from left to right) is exothermic. This is the balanced chemical equation for the reaction of sulfur dioxide with oxygen. sulfur dioxide + oxygen sulfur trioxide.