Lab #10  Stoichiometry and Solutions
 Introduction:  Stoichiometric calculations using solutions of known concentration may be carried out to predict the quantity of material that will react in a chemical reaction.  In this procedure, you will predict the volume of hydrochloric acid that will react, based on your knowledge of the amount of sodium bicarbonate used. Purpose:  To determine the volume of hydrochloric acid that will react with a known mass of sodium bicarbonate. Equipment:  Evaporation dish, watch glass, burette, graduated cylinder, aluminum foil, Bunsen burner, retort stand and ring, wire gauze. Materials: approximately 2 grams of sodium bicarbonate,  1 mol/L hydrochloric acid, distilled water. Procedure:  Prepare for this procedure by  first putting on your safety eyewear. 1. Determine the mass of the evaporation dish and the watch glass. 2. Obtain a sample of sodium bicarbonate (approximately 2 gram). Determine the mass of the sample, and add it to the evaporation dish. Distribute the sodium bicarbonate evenly on the bottom of the dish.  Cover the evaporation dish with the watch glass. 3.  Fill the burette with 1.0 mol/L hydrochloric acid. Record the volume of acid in the burette. 4.  Using a burette clamp position the burette so that its tip enters the spout of the evaporation dish. The watch glass should not block the spout. 5.    Add 4 or 5 drops of hydrochloric acid to the sodium bicarbonate through the small opening at the spout of the evaporation dish. 6.   When the reaction has stopped, add another 4 or 5 drops. 7.   Continue adding the hydrochloric acid in this manner until it no longer causes a reaction.  You may have to swirl the contents of the dish to endure that the reaction is complete. 8.   Record the volume of the hydrochloric acid in the burette. 9.   At this point, lift the watch glass, and rinse back into the dish any material which has collected on its surface. 10.  Place the evaporation dish on the retort stand.  With the watch glass removed, gently evaporate the solution.  Do not let the solution come to a boil; do not spatter material out of the dish. 11.  When only a small amount of liquid remains, replace the watch glass, and increase the heat.  Continue to heat until there is no liquid in the dish, or condensation on the watch glass. 12.  Remove the heat, and let the dish cool. 13.  Determine the mass of the dish, watch glass and product. Calculations: 1. Calculate the volume of 1 mol/L hydrochloric acid which should be used to react completely with 2 grams of sodium bicarbonate. 2.  Calculate the volume of 1 mo/L hydrochloric acid that should react with the actual mass of sodium bicarbonate used. 3.  Calculate the actual mass of the solid product produced. Questions: 1.  Compare your theoretical predictions with your actual results. Explain any discrepancies.
 Data Table Trial 1 Trial 2 Mass of Evaporation Dish and Watch Glass _________ _________ Mass of Sodium Bicarbonate Added _________ _________ Volume of Acid in Burette   i) Final Burette Reading                                               ii) Initial Burette Reading                                               iii) Volume of Acid Used _________ _________ _________ _________ _________ _________ Concentration of HCl _________ _________ Mass of Dish, Watch Glass, and Product Formed _________ _________ Mass of Product _________ _________