MKHS Chemistry 1
Lab partners ________________________________________________________
Density of CO2 from Alka Seltzer
Procedure:
1. To a 250 Erlenmeyer flask, with about 20 mL of 2M HCl solution.
2. Find the mass of the flask + water. Record in your data table.
3. Obtain a tablet of alka seltzer.
4. Mass the alka seltzer tablet and record in your data table.
5. Connect rubber tubing to the overflow stem of the trough. Connect the rubber stopper with the glass elbow and
tubing to the lower stem where the gas will enter.
6. Fill the trough ¾ way full with water.
7. Fill a 1000ml graduated cylinder with 900mL water. Record the volume of in the graduated cylinder.
8. Invert in the trough, under the water, making sure that you minimize the air bubbles getting into the cylinder.
9. When you are ready - have one person add the complete alka-seltzer tablet to the flask and quickly cap it with
the stopper (+ hose connected). Wait for the change and gas generation to proceed. *You may need to swirl
the flask to assure the change/gas generation has completed.
10. Keeping the graduated cylinder inverted, read the volume of gas collected. Record in your data table.
11. Re-measure the mass of the test tube with contents. Record in your data table. Repeat experiment.
12. Return your materials. Clean your station. Wash any waste down the sink.
Trial 1
Data (sigfigs!)
Trial 2
1. Mass of flask + 2M HCl
2. Mass of tablet (before the change)
3. Mass of flask + 2M HCl + tablet (add two masses 1 & 2 above):
4. Mass of flask + 2M HCl + tablet (after the change):
5. Mass of CO2 (gas) released: (Subtract 4 from 3 above)
6. Volume of CO2 (gas) collected:
Average Volume ____________
Average mass ___________
1. Use your data to calculate the density (m/V ratio) for carbon dioxide gas. Show your work and include units.
Experimental Density: __________
Known Density ___________
% Error __________
2. Based on the volume of carbon dioxide produced, calculate the mass of sodium bicarbonate present in the Alka
Seltzer tablet using stoichiometry. Show your work. The equation for the reaction of the sodium bicarbonate is:
HCl(aq) + NaHCO3(aq)  H2O(l) + CO2(g) + NaCl(aq)
3. Obtain the mass of sodium bicarbonate in one tablet of Alka Seltzer from the teacher.
Theoretical Yield ___________
Actual Yield ___________
% Yield __________
4. If your actual values differ from the accepted (or theoretical) values, discuss what factors may have caused this.