Purpose:
- To determine the theoretical and experimental yields for the reaction of baking soda (sodium bicarbonate) with acid to form sodium chloride of NaCl (s), carbon dioxide, CO2 (g) and water vapor, H2O(g).
- To calculate the percent yield.
Procedure:
- Weigh the evap dish.
- Weigh out approximately 0.50 g of NaHCO3 (baking soda) into the beaker and record the total mass. Add a few mL of water until the baking soda is mostly dissolved. Add a few drops of universal indicator. Record your observations
- Put about 2 mL of 1 M HCl in a grad cylinder. Add a couple of drops of universal indicator. Record your observations.
- Using a pipette, add the HCl to the NaHCO3 a few drops at a time until the reaction is complete. You will add a few drops of excess HCl. When the reaction is complete, you should not see any white powder remaining or new bubbles. Record your observations.
- Transfer your solution to the evap dish. Leave to evaporate overnight or until next class. Evaporate the solution to absolute dryness. No water droplets should be visible. Record your observations.
- When completely dry, weigh evaporating dish and product.
Data:
| Mass of evap dish | g |
| Mass of evap dish + NaHCO3 | g |
| Mass of NaHCO3 | g |
| Mass of evap dish NaCl | g |
| Mass of NaCl | g |
Equations:
1. Actual Yield of NaCl = (Mass of evap disch + NaCl)
– (Mass of evap dish)
2. Theoretical Yield of NaCl is calculated from the stoichiometry of the reaction.
3. Percent Yield = Actual Yield x 100%
Theoretical Yield
Calculated Results:
| Experimental (or Actual Yield), Mass of NaCl residue |
| Theoretical yield of NaCl: Calculate the expected amount of product for this experiment based on the reactant, NaHCO3 |
| Percent yield of NaCl |
Questions:
- Write (and balance) the equation for the reaction of sodium hydrogen carbonate with hydrochloric acid.
- Possible sources of errors have been listed below. Identify whether each of the following would lead to a percent yield that is higher than expected, lower than expected, or would have no effect. Explain why.
- Some baking soda is lost after recording the mass on the balance.
- Not enough hydrochloric acid was added to the baking soda.
- Too much hydrochloric acid was added to the baking soda.
- Some of the solution splashes out when placing it on the hot plate.
- Some of the solid product “pops” out of the beaker when heated.
- The solid product is not heated enough and water still remains.
