International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

In the process of combustion, alkanes primarily yield which of the following?

1. Only carbon products

2. Only gaseous products

3. Carbon dioxide and water

4. Carbon and oxygen

The correct answer is: Carbon dioxide and water

During combustion, alkanes react with oxygen to produce energy, carbon dioxide, and water. This is a characteristic reaction for hydrocarbons, where complete combustion occurs when there is sufficient oxygen present. In this process, the carbon atoms in the alkane are fully oxidized to form carbon dioxide, while the hydrogen atoms are oxidized to form water. This reaction typically releases a significant amount of energy in the form of heat and light, which is why it is used in various applications such as heating, powering engines, and cooking. The correct answer, therefore, reflects the main products of complete combustion of alkanes: carbon dioxide and water. Understanding this process illustrates the importance of alkanes as fuels, as they provide energy while producing only these environmentally significant products when burned completely.