Total Pressure of 2-Phase System: Dalton's Partial Pressure Law

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The discussion centers on the application of Dalton's law of partial pressures in a two-phase system, questioning whether it adequately accounts for the pressure exerted by the liquid phase. Dalton's law states that the total pressure of a gas mixture is equal to the sum of the partial pressures of its individual gas components. In a closed container with both liquid and gaseous phases, the pressure contributions from the liquid phase must be considered, particularly since hydrostatic pressure varies within the liquid. The conversation highlights the complexity of pressure calculations in multi-phase systems, emphasizing that the total pressure measurement can be influenced by the hydrostatic pressure of the liquid, which is not constant throughout the liquid column. This raises important considerations for accurately applying Dalton's law in such scenarios.
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Sum of Partial Pressures of Gas phase equals to total pressure of a 2 phase system? It sounds illogical because in a 2 phase system, the liquid phase also exerts pressure as well. Under dalton's partial pressure law, it states that the sum of total partial pressures of each gas component is equals to the total pressure of the gas.

y(i) Ptotal + y(j) Ptotal =Ptotal

If this law is applicable even to a 2 phase system, wouldn't it be inaccurate to not account for the pressure of the liquid phase also?
 
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Dalton's law describes behavior of gases.
 
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So as to state, if I have a closed container at 1 atm that has 2 component 2 phases of liquid air, liquid water and gaseous air, gaseous water, the partial pressure of gaseous water is then y(H20) x Ptotal whereby Ptotal = 1 atm. Since we are using Ptotal in the calculations, would we ignore the hydrostatic pressure caused by the liquid form as well?
 


Anyone please?
 


Hydrostatic pressure means that pressure on the bottom of the container differs from the pressure on the liquid surface. Whether you take it into account or not depends on what pressure you are calculating - it is not constant inside.
 

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