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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: BobcatBob on April 06, 2009, 08:38:02 AM

Title: Charles' Law Lab Problem
Post by: BobcatBob on April 06, 2009, 08:38:02 AM

Hi All,

I'm running a lab on Charles' Law and had some strange results that I don't understand.

Here's the basic lab setup (it's pretty standard, so maybe you're familiar with it):
1.) Heat an air-filled 250 ml flask in a water bath until temp inside flask is about 100 celsius.  Flask is stoppered with short glass tube extending.
2.) Put finger over hole in tube, remove flask, immerse inverted in colder water (about 18 celsius) and remove finger.  Water shoots into flask.

Now, Charles' Law states that about 50 ml should shoot into the flask.  Most results have been in this ballpark.  However, occasionally, we'll see the water shoot into the flask and keep flowing, sometimes almost filling the flask.

I can't figure out what's going on in these cases.  Apparently, I don't understand the concept as well as I should.

Any ideas?

Thanks,
Bob

Title: Re: Charles' Law Lab Problem
Post by: ARGOS++ on April 06, 2009, 10:55:46 AM

Dear BobcatBob;

Conclusions from the experiment:

• In the moment when the flask was sealed, then the air or almost all air was replaced by another gas at 100°C!
• The replacing gas (at 100°C) must be fully soluble in water at 18°C, or is not longer a gas at 18°C.

Do you know such a "gas" available at this particular moment with all these properties?
(There was only one around at that moment!)

Good Luck!
                    ARGOS⁺⁺