You may have noticed that water sometimes drips from the exhaust of a car as it is running. Is this evidence that there is at least a small amount of water originally present in the gasoline? Explain.

When gasoline burns in an internal combustion engine (such as in a car), it goes through a series of chemical reactions with the oxygen in the air, producing carbon dioxide (CO2), water (H2O), energy (in the form of heat), and other byproducts. The balanced chemical equation for this process can be simplified as: \[ C_8H_{18} + 12.5 O_2 \rightarrow 8 CO_2 + 9 H_2O \] This equation shows that one molecule of gasoline (represented by octane, C8H18) reacts with 12.5 molecules of oxygen (O2) to produce 8 molecules of carbon dioxide (CO2) and 9 molecules of water (H2O). Therefore, it is important to note that the presence of water is an expected product of the combustion process.

Given the information about the combustion process and its byproducts, we can now identify the source of the water observed dripping from a car's exhaust. Since water is a product of gasoline combustion, it is reasonable to conclude that the water observed comes from the chemical reaction itself, rather than being originally present in the gasoline.

Although gasoline could potentially contain some water, it is not a viable explanation for the observed water dripping from a car's exhaust. Gasoline contains a mixture of hydrocarbons and is not expected to contain a significant amount of water, nor is the water content of the gasoline sufficient to contribute to the quantity of water observed in the exhaust. Therefore, the presence of water in the exhaust is most likely due to the combustion process, which is known to produce water as one of its products. In conclusion, the observation of water dripping from a car's exhaust when it is running can be explained by the combustion process of gasoline, which produces water as a natural byproduct. There is no evidence to suggest that the dripping water comes from the presence of water in the gasoline itself.