Give me some responses to the questions below and I'll give you some extra credit.

SID#:

Laboratory Section: 1 2 3 4 5 6

1. Before injecting the sample of water into the tube on the left, indicate what is present (or not present) in the region of the tube above the level of mercury (labeled with red circle containing the number 1.)

Expert:

Their is a vacuum in the space above the column of mercury, so there are little if any particles in the vapor phase.

2. Carefully watch what is happening as the sample of water is injected into the bottom of the tube containing the mercury. Describe what you see happening. Look for the following; what happens to the first drops of liquid water as they rise to the top of the mercury column; what happens as more water reaches the top of the tube; what happens as the last bit of water reaches the top.

Expert:

When the liquid water is injected at the bottom of the column of mercury, it moves up the column of mercury because the density of water is less than the density of mercury. As it moves up the column there is some change but we'll focus on what happens as it reaches the vacuum at the top of the column. Initially pressure is very low in the region above the top of the mercury column, so the liquid water that reaches the top of the column immediately vaporizes (evaporates) because the pressure due to water is zero. As the water evaporates the pressure due to water in the vapor phase begins to increase. The first part of the water sample completely evaporates, and the liquids continues to evaporate until the pressure due to the water vapor reaches the equilibrium vapor pressure for water and condensation immediately occurs. There was enough water injected at the bottom to allow some it to completely evaporate and for some liquid water to remain.

3. At this point describe what is in the region labeled 2 in the barometer.

Expert:

At this point the region above the liquid water floating on top of the column of mercury contains water vapor. The pressure exerted by the water vapor can be determine by measuring the height of the column of mercury and subtracting that height from the original height of the column before adding the water sample. The pressure is the equilibrium vapor pressure of water at the temperature of the room (room temperature).

4. What can you say about the vapor pressure of ethyl alcohol (ethanol) compare to water at the same temperature?

Expert:

The vapor pressure of the ethyl alcohol is greater than the vapor pressure of water at the same temperature.

5. What happened to the liquid diethyl ether that was injected into the barometer? If we measured the height of the column of mercury in the barometer would that be the vapor pressure of diethyl ether?

Expert:

The initial sample of diethyl ether injected at the bottom of the column of mercury moved up the column and immediately evaporated. Since the pressure exerted by the diethyl ether vapor is less than the equilibrium vapor pressure, all the liquid evaporates. Since there is no liquid present floating on top of the column mercury at this point measuring the height of the column of mercury (and subtracting from the original height) gives a measure of the pressure due to the evaporated diethyl ether, but the measured pressure is NOT a vapor pressure.

Additional diethyl ether must be added until enough liquid diethyl ether evaporates so the pressure due to the diethyl ether vapor reaches the equilibrium vapor pressure....then condensation occurs and we can measure the vapor pressure.

6. What phase(s) must be present to be able to measure the vapor pressure of a substance in the liquid phase?

Expert:

Both liquid and vapor must be present to measure an equilibrium vapor pressure.

7. Is there anything about this animation that you feel you do not understand? List your concerns/questions.