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Prelab discussion and lab questions for Decomposition of Sodium Bicarbonate aka baking soda
Typology: Lab Reports
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Name _________________________________________________ Date _______________________ Period _________
Introduction Sodium bicarbonate is an ionic compound with the formula NaHCO 3. 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.
NaHCO 3 (s) NaOH (s) + CO 2 (g) Equation 1 NaHCO 3 (s) Na 2 O (s) + CO 2 (g) + H 2 O (g) Equation 2 NaHCO 3 (s) Na 2 CO 3 (s) + CO 2 (g) + H 2 O (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, Na 2 O; and sodium carbonate, Na 2 CO 3. 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:
____NaHCO 3 (s) ____NaOH (s) + ____CO 2 (g) Equation 1
____NaHCO 3 (s) ____Na 2 O (s) + ____CO 2 (g) + ____H 2 O (g) Equation 2
____NaHCO 3 (s) ____Na 2 CO 3 (s) + ____CO 2 (g) + ____H 2 O (g) Equation 3
Materials Balance (0.01- or 0.001-g precision) Test tube Bunsen burner Test tube clamp Sodium bicarbonate, 2.00 g Wire Gauze Spatula Ring stand with iron ring
Safety Precautions Safety goggles and aprons are required for this lab. Make sure to keep safety goggles on correctly at all times. Also remember not to point the open end of a test tube towards any person.
Procedure
Data Table
Mass (grams) Mass of empty test tube Mass of test tube + sodium bicarbonate INITIAL MASS of sodium bicarbonate Mass of test tube + solid product (1st^ heating) Mass of test tube + solid product (2nd^ heating) FINAL MASS of product Appearance of product
a. The sodium bicarbonate did not decompose completely.
b. The sodium bicarbonate was heated too fast, allowing considerable white smoke to escape from the test tube.
c. The sodium bicarbonate absorbed some moisture from the air before the experiment began and was not completely dry.