Baking Soda and Vinegar (Limiting Reactants) Lab小苏打和醋（限制反应物）实验室

Baking Soda and Vinegar (Limiting Reactants) Lab小苏打和醋（限制反应物）实验室 Baking Soda and Vinegar (Stoichiometry) Lab Theory In class, we’ve learned to compute how much of a chemical product that can be made when we mix measured amounts of reactants. In this lab, you will be actually using this information to predict how much product will be made. We will then use your theoretical value and compare it to the actual value to determine your percent yield. The reaction you will be working with should be familiar to you from the elementary science fair volcanoes: You will be mixing baking soda (NaHCO) 3 with vinegar (CHCOOH) to generate carbon dioxide (bubbles), water, and 3 sodium acetate (NaCHO) which is a food preservative. 232 Purpose To calculate the percent yield of sodium acetate using stoichiometry. Safety Please wear safety goggles at all times, be careful of loose clothing or long hair around the open Bunsen burner flame, and do not touch the Erlenmeyr flask with your bare hands after it has been heated (use a hot pad). Procedure Section 1: Computing the mass of the limiting reactant (baking soda) In this lab, you will react baking soda with an excess of vinegar. For this reaction, you need to use 0.025 moles of baking soda. In the space below, calculate the mass of baking soda (sodium hydrogen carbonate) needed: Section 2: The reaction 1. Measure out the mass of baking soda needed. Make sure to obtain this exact amount as close as you can. Record the exact amount you actually obtain. 2. Obtain and record the mass of a completely-dried 500 mL Erlenmeyer flask. 3. Then, add your baking soda to the 500 E. flask. 4. Obtain approximately 75 mL of vinegar in a beaker. 5. Add a small portion of the vinegar to the E. flask containing the baking soda. Swirl the mixture together. Continue to add small amounts of vinegar to swirl until you no longer observe bubbles. 6. When no more bubbles are observed, use a stirring rod to stir the mixture for two minutes. This ensures that all of the baking soda is dissolved. 7. Set up an evaporating apparatus using a ring stand, O-ring, wire gauze, and a Bunsen burner. 8. Evaporate the water in the E. flask using the Bunsen burner. As the water evaporates and leaves the sodium acetate, BE CERTAIN TO NOT BURN THE SODIUM ACETATE. To prevent this, once the water is almost completely evaporated, begin to move the Bunsen burner around to prevent constant heat in one area. 9. Once all of the water has been evaporated, turn off the Bunsen burner and allow the E. flask to cool. This should take approximately five minutes. 10. Once the E. flask is cooled enough, use a hot pad to mass your E. flask with sodium acetate. Record the mass. 11. Rinse your beaker with warm water and dump the contents down the drain. **Pre-lab: Go to WebAssign and complete assignment Data/Observations Create a data table based on the measurements need during lab. Calculations 1. Write and balance the equation of the reaction that we did in lab. 2. Calculate the actual yield (mass) of sodium acetate. 3. Calculate the theoretical yield (mass) of sodium acetate. 4. Calculate the percent yield of sodium acetate recovered in lab. 5. Practice problem: If we mix 50 grams of sodium phosphate with an unlimited amount of iron (III) oxide, what is the percent yield of sodium oxide if you obtain 27.4 grams of sodium oxide in lab? Questions 1. What is the connection between this lab and the material we are covering in class? 2. How did you know that a chemical reaction was taking place when you combined the baking soda and vinegar? 3. Why did you use an E. flask to combine the baking soda and vinegar? 4. Why did you heat the sodium acetate? 5. Why did you have to extra care in not burning the sodium acetate? 6. Why is it important to cool a container before measuring its mass (don’t talk about the safety issue of burning your fingers)?