CK01 Lab III-2 Observe a Decomposition Reaction--not working

[Erin Tator]

We've attempted this decomposition of sodium bicarbonate lab multiple now and are not getting a "mist" or any indication of decomposition. We are using a hotplate and a 250 mL beaker. The lab says its a 15 to 20 min lab but after heating the baking soda for 1/2 hr on medium then another 1/2 hr on high there is still no mist. We checked the temperature which varied from 90 to 110 degrees--which should be enough to cause the decomposition over that period of time so I'm wondering if our container is too big and the "mist" is just disappearing before we can observe it.

Any feedback would be appreciated.

[The Home Scientist]

That's possible. Baking soda decomposes into sodium carbonate, carbon dioxide gas, and water vapor, starting at about 100C. At 150C to 200C, the reaction occurs very quickly.

One thing you might try is heating the baking soda in a test tube rather than the beaker. The narrower mouth keeps the emitted gases better contained, and it should be easier to detect the condensed water vapor and gaseous carbon dioxide. The latter is heavier than air, so it should accumulate in a beaker, let alone a test tube.

[j yeardly]

I use an oil (cooking oil will do ) bath  and bubble through lime water (aq CaOH) ,the test for CO2  never fails