[bamster]

1. After the vapour has condensed to a liquid why is it important to obtain the weight of the liquid "without delay" in number 8?

2. What assumptions are made about the vapour of the substance in this labratory?



Lab Info

1. Weigh a clean , dry 100ml volumetric flask together with a square of aluminum foil to 4 decimal places. Record this mass in the data table.
2. Pour 3 to 5 ml of an unknown liquid into the volumetric flask. Record the unknown letter in the data table.
3. Cover the flask with the foil and make a tight seal. Make a small hole in the top of the foil using a pin.
4.Place a 600ml beaker on a hot plate and lower the volumetric flask into the beaker to within 1 cm of the bottom. Use a clamp to hold the volumetric flask in place. Pour water into the beaker to cover at least the round portion.
5. Gently boil the water in the beaker until all of the unknown liquid vapouraizes in the flask and then for about additional minutes. The total time for vapourization will be about 15 minutes.Record the temperature of the water in the data table.
6. Quickly remove the flask from the beaker and cool to room temperature by running cold water over the surface of the flask. All the vapour will condense to a liquid.
7. Dry the flask with paper towel and by blowing air over the surface.
8. Weigh the cooled and dry flask and liquid without delay. Record this value in the data table.
9. To determine the volume of the volumetric flask, fill to the top with water and pour this water into a graduated cylinder.
10. Record the the barometric pressure in the data table.

[Arkcon]

Hey Bam.

1. After the vapour has condensed to a liquid why is it important to obtain the weight of the liquid "without delay" in number 8?

2. What assumptions are made about the vapour of the substance in this labratory?

Can you use the purpose of this lab to try and take a guess and how to answer these questions?  Any guess at all.  For example, why do we do anything, outside of the laboratory, "without delay?"  We try to give hints on this forum, so people learn for themselves.  There's really no chemistry to talk about here, unless we really try to understand what this lab is about -- we have your method, what is it trying to prove?

[bamster]

The point of this lab is to determine the mass of one mole of the unknown volatile liquid.
By applying the values throughout the lab,  will be put into the Ideal Gas Equation to calculate the molar mass.

[Arkcon]

Well, then, there are some serious assumptions being made.  Can you describe them?  That would probably answer your second question adequately.