What products are obtained when CH4(g) burns completely in an excess of oxygen?

When methane (CH4) burns completely in the presence of an excess of oxygen, the process is known as complete combustion. During this reaction, methane reacts with oxygen to produce carbon dioxide (CO2) and water (H2O). The balanced chemical equation for this reaction is:

[ CH4 + 2 O2 \rightarrow CO2 + 2 H2O ]

In this equation, one molecule of methane reacts with two molecules of oxygen to yield one molecule of carbon dioxide and two molecules of water.

Understanding this process highlights several key aspects of combustion. Complete combustion occurs when there is enough oxygen available, leading to the formation of carbon dioxide, which is a stable and fully oxidized product, along with water vapor. This is in contrast to incomplete combustion, where products like carbon monoxide (CO) or even soot (C) can be formed due to insufficient oxygen.

Thus, given the conditions of excess oxygen and complete combustion, carbon dioxide and water are the definitive products produced from burning methane. This clarifies why the selection identifying carbon dioxide and water is the appropriate choice, as it accurately represents the outcome of the complete combustion of methane.