Tennessee Wastewater Operator Practice Exam

Which compound is formed when siloxanes are burned?

1. Silicon nitride

2. Silicon carbide

3. Silicon dioxide

4. Silicon tetrachloride

The correct answer is: Silicon dioxide

When siloxanes, which are a class of compounds containing silicon-oxygen bonds, are burned, they undergo a combustion process that leads to the formation of silicon dioxide. This is because, during combustion, the silicon in siloxanes reacts with oxygen from the air. The result is silicon dioxide, a common compound also known as silica, which is a significant component of sand and is found in various natural and synthetic materials. Silicon dioxide is characterized by its tetrahedral structure where each silicon atom is bonded to four oxygen atoms. This structure is quite stable and is commonly produced in various industrial processes, including the incineration of siloxanes. The other compounds mentioned, such as silicon nitride, silicon carbide, and silicon tetrachloride, are products of different reactions or processes involving silicon but are not typically formed during the combustion of siloxanes. Silicon nitride forms in high-temperature reactions with nitrogen, silicon carbide is a result of carbon reacting with silicon under specific conditions, and silicon tetrachloride is produced through a reaction between silicon and chlorine. Therefore, the formation of silicon dioxide during the burning of siloxanes stands out as the accurate outcome in this context.