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Decomposition of Sodium Bicarbonate
(Stoichiometry)
Introduction
Sodium bicarbonate is an ionic compound with the formula NaHCO3. It is also known by its common household name of
baking soda. It is used frequently for many different things, such as cooking, toothpaste, cleaning and to neutralize acids
and bases. It is also regularly utilized in refrigerators and used book stores due to its ability to absorb odors. Sodium
bicarbonate decomposes upon heating to give off carbon dioxide.
Concepts
● Moles ● Balanced chemical equation
● Molecular Formula ● Stoichiometry
Background
Sodium bicarbonate is a white solid that gradually starts decomposing at ~70ºC. The ultimate products of sodium
bicarbonate are carbon dioxide gas and a white solid. Based on the molecular formula of sodium bicarbonate, three
possible reactions (equations 1-3 below) will account for the loss of carbon dioxide gas upon heating. Note that equations
1-3 are not balanced.
NaHCO3(s) NaOH(s) + CO2(g) Equation 1
NaHCO3(s) Na2O(s) + CO2(g) + H2O(g) Equation 2
NaHCO3(s) Na2CO3(s) + CO2(g) + H2O(g) Equation 3
What is the actual chemical equation for the thermal decomposition of sodium bicarbonate? All of the possible sodium-
containing products in Equations 1-3 are real compounds: sodium hydroxide, NaOH; sodium oxide, Na2O; and sodium
carbonate, Na2CO3. All are white solids at room temperature. It is possible to determine the chemical equation for the
decomposition of sodium bicarbonate by applying the principles of stoichiometry to the masses of the reactants and the
products.
Pre-Lab Work:
1. Balance Equations 1-3 for the thermal decomposition of sodium bicarbonate.
____NaHCO3(s) ____NaOH(s) + ____CO2(g) Equation 1
____NaHCO3(s) ____Na2O(s) + ____CO2(g) + ____H2O(g) Equation 2
____NaHCO3(s) ____Na2CO3(s) + ____CO2(g) + ____H2O(g) Equation 3
