Density Of Carbon Dioxide Lab 1q623a

Determining the density of carbon dioxide Introduction Carbon dioxide gas is produced when an effervescent tablet, such as Alka Seltzer, is placed in water. This reaction occurs because three molecules of sodium bicarbonate (baking soda) plus one molecule of citric acid plus one molecule of water will transform into one molecule of sodium citrate dissolved in water, four molecules of water and three molecules of carbon dioxide gas. This creates the gas that we are using to perform this experiment. Due to density being intensive and not extensive, it will always remain the same, no matter the volume or size of the substance. The materials used this this experiment are all innocuous, meaning that there are no safety hazards to be weary of. Methods In order to find the density of carbon dioxide gas you need to be able to capture only the gas without any oxygen, nitrogen, or any other gases. We started by weighing the test tube without anything in it except a rubber stopper. Then we filled a 250ml Erlenmeyer flask to 150ml and using that to fill a test tube, but we soon realized that we wouldn’t be able to measure the volume of the gas within the test tube. Without the ability to measure the volume of the gas within the test tube there isn’t a way to find the density because the equation is mass divided by volume, thus the test is rendered unusable for a final result. We started the last two types of tests by weighing the water in the tube and weighing the tube on its own. We weighed this on a scale that was accurate to the thousandths decimal place. We also measured the volume of the water to be 13.5ml so we know that the test tube with a stopper in it contains 13.5ml water. The next method we tested was to fill a flask with 150ml of water and use a rubber stopper with rubber tubing in it to move the gas into a test tube filled with water that was submerged upside down in a 1000ml beaker. This wasn’t an effective way to do this either because carbon dioxide would go through the rubber hose as well as the air around it. The mixture of air and carbon dioxide would make the carbon dioxide’s mass be less than it usually would because the air that we breathe is less dense than carbon dioxide gas in its purest form. Again, the test was rendered unusable for the final result because of this. The final way that we did this that seemed to work better than the others; it was to fill a test tube with water and place it into a 1000ml beaker, which was also filled with water, upside down. We then dropped half a tablet of Alka Seltzer into the water and held the test tube over the gas that arose. This method was effective but it was not the most effective because we didn’t get all of the gas that some other methods could have captured. This method was the most effective out of all three because when only water was in the test tube the carbon dioxide gas could replace it without having the possibility of mixing with any other gas or liquid. The liquid was displaced by the gas and thus, only the gas remained in the container. If there was still liquid in the container we had the mass of it from before we put gas into the container so we could simply subtract the mass of the test tube and the mass of the remaining water and we would be left with only the mass of the gas. After we got the mass we poured

the water into a graduated cylinder to get the volume of the water remaining in the tube. After subtracting the remaining water from the original volume we had the volume of the gas. From here it is simple; use the equation mass/volume=density and figure out the density of the gas. This final method worked best for us because it was a way to limit the amount the air mixed in with the carbon dioxide. We got a more accurate representation of the density of only carbon dioxide and not carbon dioxide as a mixture with other elements. I think overall we used the most accurate method for testing this, even though we did not trap all of the carbon dioxide gas that was released from the half of the tablet of Alka Seltzer. That is only efficiency of gas being trapped, which does not have anything to do with the final mass or volume of the gas within the test tube and as a result does not affect the density.

Results Table 1: Final mass, volume, and density values for trials 1-3 Trial 1 2 3 Average Percent Error

Mass (g) 0.02703 0.02407 0.0462 0.03243

Volume(ml) 8.5 10.25 13.5 10.75

Density (g/ml) 0.00318 0.00234 0.00342 0.00298 50.73%

Percent Error: The results displayed in table 1 show that the results obtained from this experiment were similar to the accepted density, 0.001977g/ml, but were not precise. The percent error from the average of the three experiments is over 50%, which leads to the conclusion that the method used for collecting CO2 was not very accurate. This could have been a result of the gas within the test tube being compressed due to the water exerting pressure on the gas. This theory can also be ed by the “hissing” sound coming out of the test tube when the rubber stopper was removed. The 50% inaccuracy may have been a result of the gas being pressurized, but in the end 50% of a decimal in the thousandths place is menial, but not insignificant.