What happens when sodium bicarbonate is heated?

What are the properties of NaHCO₃ and Na₂CO₃ at high temperatures ( more than 500 K until 900 K)?
ortigosa@ari.ansaldo.it

	Vocabulary
	anhydrous

Anhydrous sodium carbonate melts at 851°C (1124 K); however, it gradually decomposes in the temperature range you've specified, according to

Na₂CO₃(s) CO₂(g) + Na₂O(s)

Sodium bicarbonate is even less stable with respect to heating. Solid NaHCO₃ begins to lose carbon dioxide and water around 100°C, with complete conversion to sodium carbonate by 200°C:

2 NaHCO₃(s) CO₂(g) + H₂O(g) + Na₂CO₃(s)

In aqueous solution, carbon dioxide production begins at room temperature and decomposition of NaHCO₃(aq) is essentially complete if the solution is brought to boiling.

The ease with which sodium bicarbonate loses carbon dioxide on heating is what makes it useful as "baking soda" and as a component in baking powders; channels opened by escaping carbon dioxide bubbles give baked goods a lighter and fluffier texture.

References

1. Y. Otsubo, K. Yamaguchi, J. Chem. Soc. Japan, 82, 557-560 (1961).

Author: Fred Senese senese@antoine.frostburg.edu

Copyright © 1997-2010 by Fred Senese
Comments & questions to fsenese@frostburg.edu
Last Revised 02/23/18.URL: http://antoine.frostburg.edu/chem/senese/101/inorganic/faq/carbonate-decomposition.shtml