Reaction Powered Car CBEE 101 Fall 2009 Hailey DeMarre, Michael Lougee, Peter Shoaf Dr. Skip Rochefort

The Alka-Seltzer Reaction Reactants: Citric Acid (aq) and Sodium Bicarbonate (aq) Products: Water (L), Carbon Dioxide (g), and Sodium Citrate (aq) Balanced Equation: C 6 H 8 O 7 (aq)+3NaHCO 3 (aq)→3H 2 O(l)+3CO 2 (g)+Na 3 C 6 H 5 O 7 (aq) Solving for the amount of reactants to use: Ideal Gas Law: P=nrT/v => Pv/rT = n The pressure was supposed to be about 5 atm; P=5 atm. The gas constant is always the same; r= atm-L/mol-K. The outside temperature was about 7 degrees C, or 280K; T=280K. The volume of the Propel bottle is 700 mL filled with 200 mL of water; v=0.5L. EXAMPLE CALCULATION: n = (5 atm)(0.5 L)/[( atm-L/mol-K)(280 K)] n = mol CO 2 ( mol CO 2 )(1 mol NaHCO 3 /1 mol CO 2 )(0.845 g NaHCO 3 /1 mol NaHCO 3 )=9.139 g NaHCO 3 ( mol CO 2 )(1 mol C 6 H 8 O 7 /3 mol CO 2 )(0.136 g C 6 H 8 O 7 /1 mol C 6 H 8 O 7 )=4.930 g C 6 H 8 O 7 These calculations show how much of each reactant should be used in order to obtain enough pressure to PROPEL the car.

Car Design The design is very simple, optimizing weight. Only 4 wheels, axels, middle support, and the bottle, held on by low weight hair ties.

Testing Results TrialSodium Bicarbonate (g)Citric Acid (g)Water (mL)Distance (ft) Trials 8, 9, and 10 are the official testing trials. Trials 1 through 7 were done without instructor supervision

Conclusions Performance: –Distance varied a lot. Mostly due to changes in the way the reactants were added together and amount of water used. –The amount of reactants used was not conjoint with the calculations for 5 atm. We did not wait long enough for all of the reactants to be used because the bottle was leaking. Some of the reactant amounts that were used were calculated using the total volume of the bottle, not considering the volume of water. Redesign: –Would use the same simple and lightweight design. –Maintain consistency of amount of reactants used. –Use a container that didn’t leak under pressure as easily. –Wait for the reactants to fully react before releasing pressure.