Students combine sodium carbonate and hydrochloric acid generating carbon dioxide gas which is allowed to escape. They measure the actual yield of carbon dioxide produced (missing mass), calculate the theoretical yield using stoichiometry, and then the percent yield. Students understand that 100% yield is the most appropriate answer (based on the Law of Conservation of Mass), so after considering the meaning of significant figures and the uncertainty of their measurements they are asked to decide if they did (or did not) get an answer that might indicate the validity of the Law.
One 50-minute period to perform the lab. One additional period to perform the calculations (optional). Often more able students will have time to begin some calculations at the end of the lab experiment.
Fostering Engagement in Nanotechnology
The Feburary 2014 issue of the Journal of Chemical Education is now available online to subscribers at http://pubs.acs.org/toc/jceda8/91/2. The February issue features articles on nanotechnology in the areas of public engagement, instrumentation, and laboratory experiments.
Changing the Landscape of Chemical Education
The December 2013 issue of the Journal of Chemical Education is available online to subscribers at http://pubs.acs.org/toc/jceda8/90/12. This issue of JCE plus the content of all past issues, volumes 1 through 90, are available to subscribers at http://pubs.acs.org/jchemeduc.