Name: __________________________ Section: _____ Date: _______________ Lab Partner: _____________________ Baking Soda Stoichiometry Prelab Questions Baking soda (sodium bicarbonate is a common ingredient in baked goods. What is the formula for sodium bicarbonate? What state of matter is sodium bicarbonate? When baking soda is heated, it breaks down into new compounds. This is an example of what kind of reaction? If you omit baking soda from a recipe, the final product’s texture isn’t as light and fluffy as you would expect it to be. What does that tell you about the state of at least one of the products from the reaction? Background In this experiment, you will use stoichiometry to determine which of the three reactions takes place when baking soda is heated. 1. Sodium bicarbonate sodium hydroxide + carbon dioxide 2. Sodium bicarbonate sodium oxide + carbon dioxide + water 3. Sodium bicarbonate sodium carbonate + carbon dioxide + water Before completing the experiment, determine the complete balanced equation for each of the possible reactions above, including the states of each compound involved. 1. 2. 3. Materials Sodium bicarbonate Bunsen burner Ring stand Iron ring Clay triangle Balance Crucible Crucible tongs Procedure 1. Make sure the crucible is clean and dry. 2. Use the balance to find the exact mass of the crucible. Record the mass in the data table. American Association of Chemistry Teachers 1 3. Place about 2 grams of baking soda in the crucible, and weigh the crucible containing the baking soda on the balance. Be sure to record the exact mass you obtain. Do not zero the balance with the empty crucible on it—you need to know the total mass of the crucible with the baking soda in it. 4. Heat the crucible with the Bunsen burner for about 10 min. You can use a stirring rod or spatula to stir the powder and break up any clumps that form. 5. Remove the crucible from the heat and allow it to cool. When it is cool to the touch, find the mass of the crucible and the solid in it. Record this mass. 6. When you are finished, wash the contents down the sink with lots of water. Clean and dry the crucible and any other equipment you used. 7. Data Material(s) 1. Empty crucible Mass (g) 2. Crucible with baking soda (before heating) 3. Mass of baking soda (subtract line 1 from line 2) 4. Mass of crucible with solid in it (after heating) 5. Mass of solid (subtract line 4 from line 1) Calculations 1. From the background, what are the three possible reactions you could have witnessed in this experiment? 1. 2. 3. 2. Calculate the number of moles of baking soda you started with. Show your work! American Association of Chemistry Teachers 2 3. For each reaction equation in question 1, calculate what mass of solid product you would expect to have after decomposing the sodium bicarbonate. Show your work, including the mole ratios you used! 1. 2. 3. 4. Compare the results of your calculations to the mass of the solid in your data table. According to your data, which equation properly expresses how baking soda decomposes? 5. Check with your teacher to find the actual reaction that took place. Were you correct? If not, what do you think went wrong? 6. You probably didn’t get exactly the same amount of solid as you calculated. Find your percent difference using this equation: predicted grams of solid-actual grams of solid percent difference= ×100 predicted grams of solid 7. Did you get more or less than what your calculations predicted? What are some possible reasons for the difference? Conclusion What did you learn from this experiment? American Association of Chemistry Teachers 3