Bubble point and dew point temperatures
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Are the bubble point and dew point temperatures equal? If they are equal, under what circumstances are they equal?
For general mixture systems, the bubble point and dew point are not equal. At vapor-liquid equilibrium, the dew point of the vapor phase is the bubble point of the liquid phase. When a pure substance is in equilibrium, the compositions of the vapor and liquid phases are identical, and the dew point equals the bubble point. However, at equilibrium, the compositions of the vapor and liquid phases in a mixture are generally not the same. Therefore, the dew point and bubble point of a mixture with a fixed composition are not equal.
The dew point and bubble point of a pure substance are equal.
For general mixtures, the bubble point and dew point temperatures are different, while for pure substances they are the same
The bubble point, also known as the boiling point, is the temperature at which a liquid mixture begins to vaporize and the first bubbles appear when the mixture is heated under constant pressure; it is simply referred to as the bubble point. Dew point, also known as dew point temperature, refers to the temperature at which a gas mixture is cooled under constant pressure until the first liquid droplets begin to form in the mixture; it is simply called the dew point. For a pure substance, at a certain pressure, its bubble point temperature is equal to its dew point temperature, which is also its boiling point.
There is such a principle at play: to change from a liquid to a gas, it is necessary to overcome surface energy; therefore, shouldn’t the bubble point be higher than the dew point?
The bubbling point temperature should be less than or equal to the dew point temperature, right?
The bubble point and dew point of a pure substance are the same, while those of a mixture are equal only when gas-liquid equilibrium is reached.
It becomes clear by looking at the two-component phase diagram; when the pure components are equal
The bubble point temperature and dew point temperature of a pure substance are the same, whereas for a mixture, the dew point temperature is higher than the bubble point temperature.