Sulphur dioxide is a compound and oxygen is in elemental form. They combine to form sulphur trioxide.
A combination reaction is a general category of chemical reactions. It may be defined as a chemical reaction in which two or more substances combine to form a single substance under suitable conditions. Similarly, non-metals may react with highly active metals to form covalent compounds. Combination reactions involve the formation of new bonds and this process releases a large amount of energy in the form of heat.
- Sulphur reacts with oxygen gas to form gaseous sulphur dioxide
- Carbon monoxide reacts with oxygen gas to form carbon dioxide.