For the experiment the total volume of the liquid must equal 40.0 mL for each trial. Fill in the following data table to indicate the amount of water to be added to the vinegar. Volume of Vinegar (mL) Volume of water (mL) 0.0 5.0 10.0 25.0 30.0 Use the following data to answer the questions… Vinegar (mL) Water (mL) Mass liquid in beaker (g) A Mass Alka Seltzer Tablets (g) B Mass beaker & contents before rxn. (g) A + B Mass of beaker & contents after rxn. (g) C Mass of CO2 (loss of mass) (g) (A + B) – C 5.0 35.0 145.0 3.23 148.23 147.60 0.63 20.0 20.0 148.0 3.27 150.12 Fill in the missing data from the second trial. To determine the mass of NaHCO3 in the Alka Seltzer tablet, you must use a stoichiometric calculation in which you start with the mass of CO2 produced and determine the amount of NaHCO3 that must have reacted to produce that. Find the mass of NaHCO3 in each tablet given in the data table above. (Hint: Stoichiometry: Mass of CO2 to Mass of NaHCO3) Trial 1: Trial 2: The % NaHCO3 in each Alka Seltzer tablet can be determined by dividing the grams of NaHCO3in the tablet (your answers from 5b) by the total mass of the tablet (from the data table). Find the % NaHCO3 for each tablet in the data table above. Trial 1: Trial 2:
Procedure: Record the amount of vinegar you and your partner will be testing here: _____mL &____mL and in data Table 1. Measure the first amount of vinegar using a graduated cylinder and pour into a 250 mL beaker. Measure the amount of water you would need to add to make the total liquid volume = 40.0 mL using a graduated cylinder and pour into the same 250 mL beaker; stir. Record the mL of water in data table 1. Mass the beaker w/liquid and record in data table 1. Mass an Alka Seltzer tablet and record in data table 1. Place the Alka Seltzer tablet into the 250 mL beaker w/water. When the bubbling has stopped, stir the solution to make sure the tablet has completely dissolved and to remove any visible bubbles of carbon dioxide. Gently tap the stirring rod against the inside of the beaker to remove any drops of liquid. Mass the beaker and its contents. Record the mass and record in data table 1. Dispose of the solution in the beaker down the sink and wash the glassware! Data: Table 1: Partner Data A B A + B C (A + B) - C Exp. # Volume of Vinegar (mL) Volume of Water (mL) Mass of beaker & liquid (g) Mass of Alka Seltzer tablet (g) Total mass of beaker and contents before rxn. (g) Total mass of beaker and contents after rxn. (g) Mass of CO2 lost (g) Mass of NaHCO3 in tablet (g) % NaHCO3 in tablet ((mass tablet) x 100) 1 2 Calculations: Show ALL of your calculations used to complete Data Table 1. Trial 1: Trial 2:
Data: Table 2: Class Data Volume of Vinegar (mL) Volume of Water (mL) Mass of beaker & liquid (g) Mass of Alka Seltzer tablet (g) Total mass of beaker and contents before rxn (g) Total mass of beaker and contents after rxn (g) Mass of CO2 lost Mass of NaHCO3 in tablet (g) % NaHCO3 in tablet (mass NaHCO3/mass tablet) X 100 0.00 40.00 197.9 1.68 199.29 0.29 5.00 35.00 147.04 1.36 148.10 0.30 10.00 30.00 194.43 1.35 195.41 0.37 15.00 25.00 196.6 3.20 197.75 0.52 20.00 20.00 197.95 2.02 99.32 0.63 25.00 15.00 145.07 2.13 146.24 0.62 25.00 15.00 147.42 1.65 148.65 0.48 30.00 10.00 147.21 1.83 148.50 0.55 Analysis Questions: Why must the mixture in the beaker be stirred after the reaction is completed? Which substance (Alka-Seltzer OR Vinegar) do you think was used up in the reaction? Explain why. Explain TWO sources of error that could have occurred in this lab and how each would affect the results. On the back, create a bar graph using the % of reacted NaHCO3 (Y-axis) versus the volume of vinegar used X-axis) to determine if you were correct in your identification of the limiting reactant in this reaction. Be sure to include a title, key and label your X & Y AXIS. Look at the class data for % NaHCO3 vs. mL vinegar used. What trend do you notice?