Lab 1.1
decom position of sodium bicarbonate
Introduction
Baking soda is a common food additive. It is useful because when heated to a few hundred degrees
Fahrenheit, it decomposes. Some of the products of this decomposition reaction are gases, and these gases
help foods such as cookies and pancakes “rise,” creating pockets of trapped gas in the food structure so that
it is less dense.
In this lab, you will examine the reaction quantitatively. Based on your experimental data, you will be
able to conclude which of several possible sets of products form s when sodium bicarbonate decomposes. In
words, the possible reactions are:
I.
sodium bicarbonate
(solid)
º
sodium hydroxide + carbon dioxide
(solid)
(gas)
II.
sodium bicarbonate
(solid)
º
sodium oxide + carbon dioxide + water
(solid)
(gas)
(gas)
III.
sodium bicarbonate
(solid)
º
sodium carbonate + carbon dioxide + water
(solid)
(gas)
(gas)
IV.
sodium bicarbonate
(solid)
º
carbon + sodium + hydrogen + oxygen
(solid)
(liquid)
(gas)
(gas)
CAUTION!! The heated crucible will remain hot for a considerable time. It is not possible to tell
visually whether the crucible is hot. You should not touch the crucible during the
lab— both to protect you from burns, and to avoid contaminating it.
Pre-lab questions (complete these in your lab notebook)
1. W rite a balanced reaction equation for each of the four reactions shown in words above.
2. For each of the four balanced reactions, determine the mass of solid product produced when 1.0000 g of
sodium bicarbonate is decomposed. Show your work fully.
Procedure (in your lab notebook, cut/paste this procedure, or summarize it)
1. Clean a copper crucible with detergent and water. Rinse with tap water, then distilled water.
2. Strongly heat the crucible over a flame. Move the flame so that all parts of the crucible are dry and
evenly oxidized (black).
3. Let the crucible cool. Do not touch the hot crucible.
4. Meanwhile, pre-weigh between one and two grams of sodium bicarbonate in a weighing dish.
5. Using tongs, place the cooled crucible on an analytical balance. Record its mass, then add the preweighed bicarbonate (without taring the balance) and record their com bined mass.
6. Using tongs, transfer the crucible to the clay triangle and heat it strongly for at least ten minutes. Midway
through the heating, you m ay want to use the spatula to stir the solid and break up any clum ps.
7. Remove the flame and allow the crucible to cool.
8. Using tongs, transfer the crucible to the analytical balance and record the final mass.
9. Em pty the residue from the crucible and clean it as in step 1.
Data
Prepare a data table in your lab notebook to contain the data you will collect. Also record any
observations here during the experiment.
Calculations
Repeat calculations like those in pre-lab question two for your actual experimental data.
Lab report
Prepare a report on separate paper (i.e. not in your lab notebook). Include a brief introduction, data,
balanced reaction equations, calculated results (including work), and a brief conclusion that clearly states
which reaction you believe occurred. Support this conclusion with specific experimental evidence.
Comment on the relative size of any error and its possible causes.
©Deerfield High School
AP Chem istry
1-1