The Solubility of CO2

Instructions on how to find the solubility of carbon dioxide.It also contains results from when I ran the experiment as well as discussion about the experiment.

Question: what is the solubility of CO2 in water?

Materials:

  • 2 commercial soluble-in-water antacid tablets (Alka Seltzer ™ is used here)
  • 1 bucket
  • 1 bin
  • Lots of water
  • Tubing
  • Bent glass tube
  • 500 ml flask
  • 125 ml flask
  • Stopper for 125 ml flask with hole and stopper for 500 ml flask without hole

Setup:

Fill a bin about half way with water. Next, fill up the 500 ml flask with water, stopper it, and unstopper it upside down under the water of the bin. Do not let any air into the flask. Next take the bucket and fill it with 1440 ml of water because the flask in its entirety holds 560 ml, and we want to keep the 1500 ml system. Now put the bent glass tube into the rubber tube and also into the small stopper. Fill up the 125 ml flask about halfway. Crack the Alka seltzer tablets in half. Now put the tube into the water. Congratulations, you are done setting up. Give yourself a nice big hug (not required).

Procedure

Put the four tablet halves into the 125 ml flask and quickly stopper. After about 2 seconds put the tubing into the upturned flask. Fill the flask with the CO2 until it reaches the 500 ml mark and stop filling. Stopper the flask and transfer to the bucket. Unstopper the flask upside-down under the water in the bucket. Swirl for about 15 minutes, being careful not to let any gas escape. Then check the water level. The number on the flask that the water level goes up to minus 500 is the negative amount of gas dissolved. For instance, if the water level goes from 500ml to 450 ml, then 50 ml of gas has dissolved. Now record the amount of gas dissolve. Multiply this by 0.002, the density of carbon dioxide, and that number will be the mass of the gas dissolved. Now take that number and divide it by 1500. The result is the concentration of CO2 in the water. Record this. Next make sure the flask will not tip over and being sure to leave a small opening underwater leave overnight. Come back in the morning and look at and record how high the water has risen. Repeat the steps above for calculating the concentration but not from your old measurement but still from 500. Now you have what may be the solubility of carbon dioxide. Record this. Congratulate yourself.

Observations:

When we first swirled the flask for fifteen minutes, we saw that the water level went from 500 ml to 400 ml, corresponding to 100 ml of gas dissolving. We multiplied this number by 0.002 and got 0.2 grams of gas. We then divide this by 1500 ml and found that to significant figures that the concentration o the carbon dioxide was 0.0001 grams per ml.

The next day we found that the water had risen to 100 ml. we redid the steps above, but this time using 400 ml of gas instead of 100ml and we found that the concentration was at that time 0.005 grams per ml.

Answer to question:

We believe that that the solubility of carbon dioxide in water is 0.0005 grams per ml
(that is the result of this experiment. The actual solubility of carbon dioxide

Discussion:

Why did we swirl the flask for 15 minutes? We did that because we wanted to give the gas access to fresh, non-saturated water.

Is our water saturated? We don’t know for sure, I believe so though because of the amount of time we gave it to dissolve.

How can we tell this? We can tell this possibly by taking the water in the flask and rerun the experiment on a smaller scale using it. If nothing happens when we leave it overnight and come back, we will know that the water s saturated.

Why did we switch between the bin and the bucket? We switched between the bucket and bin because we did not want to use the water that we bubble the gas through because it might have gas already dissolved in it. Also, we know how much water is in the bucket but not the bin.

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2 Responses to “The Solubility of CO2”
  1. stfa Says...

    On September 7, 2009 at 7:27 am

    Pah what a silly report


  2. Peter Says...

    On January 27, 2010 at 11:24 am

    Thank you for this experiment. It is very simple, but quantitative. A few suggestions. It might be good to demonstrate that the gas you are dealing with is carbon dioxide by showing, for example, that a match will go out when it is dipped in it. Also, it might be useful to mention that the solubility varies with the temperature, and pressure. I was trying the same experiment myself, but was getting no results, so was glad to come across this. What I had read from books is that water absorbs an equal volume of carbon dioxide gas. That would generally mean that it absorbs the same as the density of the gas, which is about 2g/l at stp, or .002g/ml. Since the solubility of gas decreases with increasing temperature over a certain range, your number, about a quarter of the one I mentioned, lends credibility to published measurements. But I just wonder what you might add to your experiment to make me completely abandon my faith in the published numbers and rely on yours.


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