Na2CO3 is sodium carbonate. Like most metal carbonates it undergoes thermal decomposition to produce carbon dioxide. Here's the equation:
`Na_2CO_3 -gt Na_2O + CO_2`
Sodium carbonate absorbs water to form a decahydrate, meaning that each molecule is associated with 10 water molecules. As it's heated it begins to dehydrate, or lose water molecules to form the anhydrous compound. The anhydride begins to gradually decompose to CO2 and Na2O at a temperature near its melting point of 851ºC. However, it can be melted. Molten sodium carbonate is used as flux in glass production.
The pattern for the thermal decomposition of carbonates is the production of CO2 and an oxide of the metal. Baking soda, a similar compound, is less stable and decomposes at a lower temperature to produce CO2, Na2O and water. Calcium carbonate is heated to produce the calcium oxide used in cement through a similar chemical reaction.