What on the PT chart indicates a zeotropic blend when bubble point and dew point values are present?

What on the PT chart indicates a zeotropic blend when bubble point and dew point values are present?

• A. Bubble point values present
• B. Dew point values present
• C. Temperature glide only
• D. Bubble point and dew point values

Answer: (D)

Zeotropic blends show a temperature glide during phase change because the components boil at different temperatures, so the liquid and vapor compositions evolve as boiling occurs. On a PT chart, this means you can read both a bubble point temperature (where the liquid just begins to boil) and a dew point temperature (where the vapor just begins to condense) at the same pressure. Seeing both bubble point and dew point values indicates the mixture has distinct boiling and condensing temperatures, which is the defining sign of a zeotropic blend.

Zeotropic blends show a temperature glide during phase change because the components boil at different temperatures, so the liquid and vapor compositions evolve as boiling occurs. On a PT chart, this means you can read both a bubble point temperature (where the liquid just begins to boil) and a dew point temperature (where the vapor just begins to condense) at the same pressure. Seeing both bubble point and dew point values indicates the mixture has distinct boiling and condensing temperatures, which is the defining sign of a zeotropic blend.