If steam has a quality of 98%, what does it mean regarding its composition?

A steam quality of 98% indicates that the steam is made up of 98% vapor and 2% liquid water. In this context, "quality" is a measurement used to describe the proportion of steam in a mixture of water and steam. When the quality is expressed as a percentage, it represents the amount of vapor present relative to the total mass of both the vapor and the liquid.

In this case, a quality of 98% means that out of a total of 100 parts of the mixture, 98 parts are in the form of steam (vapor), and the remaining 2 parts are in the form of liquid water. This high quality indicates that the steam is mostly vaporized, which is generally desirable in many applications, such as in steam engines or turbines, where the presence of excessive liquid can cause inefficiencies or damage.

The other options do not accurately reflect the definition of steam quality. For instance, the idea that it could be 98% liquid contradicts the definition of high-quality steam, while complete vaporization would imply 100% quality. The suggestion of a mixture containing oil is also irrelevant to the context of steam quality, which specifically pertains to the vapor-liquid composition of water and steam.