Making Water Shakhashiri has all the answers. I like to do the demonstration of a neutralization reaction with equal volumes of hydrochloric acid and sodium hydroxide. The reaction produces salt and water. If you mix 500 milliliters of 2-molar solutions of the acid and base, you will produce 18 mL of water (1 mole). I learned about this demo at ChemEd, a great conference for chemistry teachers. In previous years, I used a 1-liter graduated cylinder, my favorite demonstration glassware, for this reaction. Although it always worked, the additional volume of water was very difficult to see. Shakhashiri has a description of this same demo in volume 3, Demo 9.17, with the solution to my problem. He uses volumetric flasks! Of course! Today, when I combined the 500 mL of acid and base, both made up in 500 mL volumetric flasks, the additional water was easily visible in the neck of a 1-liter volumetric flask. I added some universal indicator to the acid and base solutions to give the demo some color. This was an extra bonus because the two solutions formed layers when I poured them together the 1-Liter flask. We all enjoyed the interesting effect of the blue and pink layers. When I mixed the flask, the volume increase caused pressure to build up in the flask and the stopper popped off a couple of times. Overall, the Demo was a great way to show the products of a neutralization reaction, including the often-overlooked water molecules that are formed.
Posted on: Thu, 14 Aug 2014 08:09:43 +0000
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