How does water vapour affect Charles' law results in a freezer experiment?

[Myr73]

I am working on a lab, that was to test charle's law. In order to do so, I filled a conainer with salted water, that had a pippette taped on the inside of it. I then inserted it in the freezer and observed it's temperature as the water volume rose in the pippette. I then took the volume of water data and found the volume of air in the pipette by subtraction .After creating a graph of volume air versus Temperature, I extrapolated the graph in order to find what the estimate Temperature would be at Volume zero of air.

My answer was -160C , of course we all know the correct temperature is -273.15C.

Now I have to explain what the possible erros are, I have most, however the instructions said to explain how the water vapour in the air could be affecting the calculations. And to estimate how much it could be affecting the calculations.

 

[dauto]

Don't just say I calculated X and it turned to be equal to -160. Show us your calculations. It's impossible to help you if you don't show your work

 

[Myr73]

The graph was extrapolated. It's not really about the answer, the answer is expected to be wrong. The question is to explain why the answer would not be exact. Like what are the lab limitations. I have most of the limitations found. Except for the part about why and how the water vapor would affect the calculated data. That is, why would it affect the volume of air in the pipette. The volume of air was found by subtracting the volume of the pipette by the volume of the water in the pipette for every given amount.

 

[interhacker]

The water vapor can give larger than actual measurements for the volume of air since water in vapor form doesn't get subtracted from the total volume.