[Chemistry] Vapor pressure of water at temperature

In summary, the conversation is about a lab where the goal is to find the vapor pressure of water. The known data includes the temperature of the system, the volume of trapped air, and the atmospheric pressure. The student is unsure how to differentiate between pressure from the temperature of the air and pressure from the temperature of the water. They also mention using the equations pv=nRT and Pair=Ptotal-PH20 to find the pressure of the air and water. They are not allowed to use outside information for the lab. At the end, the student thinks they may have figured it out by using atmospheric pressure as equal to total pressure inside the bubble and using the equation P_h20=Atmospheric pressure - P_air.
  • #1
RossH
75
0

Homework Statement


Hi. I'm working on a lab in which I must find the vapor pressure of water. Data that I know is the temperature of the system, the volume of trapped air (2.35 mL), and the atmospheric pressure (1.024 atm). This means that I have 1.1x10^-4 mol of trapped air.

Beyond this, I took temperature and volume readings of the system at 5 deg C intervals as it cooled from 80 deg C. So at 80 deg C I know that the volume of the trapped air was 5.85 mL. The problem is that I am not sure how to differentiate between pressure from the temperature of the air changing and pressure from the temperature of the water changing.


Homework Equations


I know that pv=nRT. I am using a value of R=0/082Latm/Kmol.
I know that Pair=Ptotal-PH20.


The Attempt at a Solution



So my big question is if the temperature of the water outside of the system is changing, does this mean that the pressure of the air and the pressure of the water will change? Or is the pressure a function of pv=nrt as with the information that I found in the beginning? I'm obviously not allowed to use any information from the internet other than these equations, since this is a lab. Thank you for any help that you ca give.
 
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  • #2
I think I might have figured it out. Is this it: atmospheric pressure is always equal to total pressure inside the bubble? Then I would use pv-nrt to figure out P_air and P_h20=Atmospheric pressure - P_air. Is this correct?
 

FAQ: [Chemistry] Vapor pressure of water at temperature

1. What is the significance of vapor pressure in chemistry?

Vapor pressure is an important concept in chemistry as it is a measure of the tendency of a substance to escape into the gas phase from its liquid or solid phase. It is used to understand the behavior of liquids and solids at different temperatures and pressures, and is crucial in processes such as distillation and evaporation.

2. How is vapor pressure of water affected by temperature?

The vapor pressure of water increases with increasing temperature. This is because at higher temperatures, the molecules of water have more kinetic energy and are able to overcome the attractive forces holding them in the liquid phase. This leads to a greater number of water molecules escaping into the gas phase, resulting in higher vapor pressure.

3. What is the relationship between vapor pressure and boiling point of water?

Vapor pressure and boiling point are directly related. As the vapor pressure of water increases, the temperature at which it boils decreases. This is because at higher vapor pressures, less heat is required to overcome the atmospheric pressure and allow the water to enter the gas phase. Therefore, at higher vapor pressures, the boiling point of water is lower.

4. How does altitude affect the vapor pressure of water?

As altitude increases, the atmospheric pressure decreases. This results in a decrease in the vapor pressure of water as there is less pressure pushing down on the liquid, making it easier for water molecules to escape into the gas phase. This is why water boils at lower temperatures at higher altitudes.

5. How is the vapor pressure of water measured?

The vapor pressure of water can be measured using various techniques such as the isopiestic method, which involves measuring the vapor pressure of water in equilibrium with a known solution, or the static method, where the vapor pressure is measured directly by collecting the gas above a liquid sample. Other methods include the dynamic method and the boiling point method.

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