How Does Dew Point Change in a Gas Mixture of Different Proportions?

AI Thread Summary
The discussion focuses on how the dew point changes in a gas mixture under compression. When compressing a mixture of gases A and B, each with different condensation pressures, the dew point will depend on the proportions of each gas in the mixture. Raoult's law is referenced to explain the relationship between vapor and liquid phases at equilibrium, indicating that the total pressure must be sufficient for condensation to start. The minimum pressure for condensation is derived from the mole fractions of the gases and their respective equilibrium vapor pressures. Understanding this behavior is crucial for applications involving gas mixtures and their phase changes.
Pash
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Dear All...
For my first post in this forum I have choosen an easy question for you all!

If I have a gas at room temperature and I start to compress it, when the gas reach its dew point, condensation starts

What about for a gas mixture?? I try to be clear!

I have two real gasses: A & B.
At room temperature the gas A condenses at 10bar, the gas B at 100bar.

What happens if I start to compress a mixture of 50% of gas A and 50% of gas B?

And if I change the mixture?? for example 20%-80% or 80%-20% of gas A-B respectively?

At the present I was not able to understand if this is an easy question with very difficul application or directly a difficult question!

Thanks!
 
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Raoults law says that, when vapor and liquid are at equilibrium $$P^*x=py$$ for each species, where P* is the equilibrium vapor pressure at the temperature, x is the mole fraction in the liquid, y is the mole fraction in the vapor, and p is the total pressure. So, a bicomponent mixture of A and B at vapor-liquid equilibrium, $$x_A=\frac{py_A}{P^*_A}$$and $$x_B=\frac{py_B}{P^*_B}$$At the condensation point, the pressure p must be high enough for the mole fractions in the liquid to add up to 1: $$x_A+x_B=\frac{py_A}{P^*_A}+\frac{py_B}{P^*_B}=1$$So, the minimum pressure required for condensation to begin is $$p=\frac{1}{\left[\frac{y_A}{P^*_A}+\frac{y_B}{P^*_B}\right]}$$
 
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