Reaction Powered Car Chelsey Chapman Mallory Goff Brian Livingston Group Picture: Chelsey C, Mallory G, Brian L Reaction Chemistry: Theoretical Predictions • H3C6H5O7 (aq) + 3NaHCO3 → 3CO2 (g) + 3H2O (l) + NaC6H5O7 (aq) • 1 Tablet of Alka-Seltzer contains 1 gram of citric acid and 1.916 grams of sodium bicarbonate (baking soda) • (1g citric acid)/(136 g/mol) = 0.00735 mol citric acid per tablet • (1.916g baking soda)/(48g/mol) = 0.0400 mol baking soda per tablet • Using 6 tablets: – (6*0.00735 mol citric acid)/(3 mol CO2/1 mol citric acid) = 0.1323 mol CO2 – P=nRT/V P=(.1323 mol CO2)(.08205 L*atm/(mol*K))(273 K)/0.600 L = 4.94 atm • Using 5.5 tablets, the pressure in the bottle is 4.53 atm • Using 6.5 tablets, the pressure in the bottle is 5.35 atm • Using 7 tablets, the pressure in the bottle is 5.76 atm Car Design Testing Results: Data + Plots Distance Car Traveled (feet) Practice Runs with 100 mL of Water Practice Trials Data Table: 35 30 25 20 15 10 5 0 0 2 4 6 8 # of Alka-Seltzer Tablets amount of water used (mL) Distance (ft) 8 8 7 6.5 6.5 6 100 100 100 100 100 100 30 4 28 18 22 15 10 # of Alka-Seltzer Tablets Used in Reaction Testing Trials Data Table: # of Alka-Seltzer Tablets amount of water used (mL) Distance 6 100 180 in - out (9.8 ft) 6 100 out 6 100 out Conclusion: Performance and Re-Design Ideas Performance: In trial runs, our car perform fairly consistently with good results. On the day of the finals, our car did not perform as it did previously. We believe this is because the plastic had bent overnight beneath the pressure of the water bottle and rubber bands. We re-designed it towards the end of the finals but the new lightweight design could not withstand the acceleration that our previous design could. Because we were not able to practice consistently on this new design, it spun out of control on all three runs during the competition. Re-Design Ideas: A lightweight design with the propel bottle positioned lower to the ground. To compensate for the new design, less tablets and water would need to be used. It would also be beneficial to make sure the wheels could move freely and travel in a straight line by allowing them more room to spin.