ENTHALPY OF FORMATION: Combustion of Methanol River Dell High School Team A Jason Anesini Alina Kim Jae Noh
PURPOSE To construct an alcohol/hydrocarbon-fueled combustion reactor that propels a stopper upwards To determine the optimal way of measuring the energy released in the combustion reaction To determine the enthalpy of formation of methanol
EVERYDAY COMBUSTION Fireworks Charcoal Car engines Gasoline
COMBUSTION What is combustion? CH3OH(l) + 3/2O2(g) CO2(g) + 2H2O(g) Exothermic Reaction Endothermic Reaction Energy released ∆Hp < ∆Hr -∆Hrxn Energy absorbed ∆Hr < ∆Hp +∆Hrxn
EXOTHERMIC VS. ENDOTHERMIC
ENTHALPY Heat of formation Heat of combustion ∆H when one mole of a compound is formed from its elements Standard heat of formation Heat of combustion Heat released in a combustion reaction
METHANOL STRUCTURE
METHANOL Synthesized from CO and H2 Used as energy source and in many everyday appliances Lowest Ea among alcohols Costs 3x less than ethanol Memorize everyday supplies
EXPERIMENT APPARATUS Stopper – with green line Methanol (stored in Drierite) Nalgene bottle (500 mL) Insulation Bubble wrap Glass fiber Tesla coil Copper wires Drierite is anhydrous calcium sulfate (check) Goes from blue to white (hydrous state)
EXPERIMENT APPARATUS Rubber Stopper Tesla Coil Methanol and Drierite Nalgene Bottle (500mL)
MEASUREMENT APPARATUS 120 f.p.s camera (Sony HDR-SR11) Meter stick Thermometer Laptop Temperature probe Vernier Software: Logger Pro 3.8.4
KINETIC ENERGY E = 1/2mv2 Mass of cork (w/ line) before reaction Film: observe frame-by-frame to find initial velocity
KINETIC ENERGY Frame 987 Frame 988
HEAT ENERGY q = mCp∆T Variable Air in Bottle Bottle Mass Volume of bottle and density of air Mass of bottle (without copper wires and insulation) Specific Heat (Cp) At the average temperature of 300C Specific heat of LDPE Temperature Change (∆T) Thermometer Temperature probe (laptop) Separately discuss insulation if necessary
RESULTS Total energy: kinetic energy & heat energy Cork Air in bottle Bottle Heat energy represented the majority of total energy Equations in appendix were imported into Excel to make the spreadsheet
DATA TABLE
DATA ANALYSIS Experimental ∆Hf of methanol: -535kJ/mol Theoretical ∆Hf of methanol: -238.4kJ/mol 124% error Small ∆Hc results in large experimental ∆Hf ΔHc = [ΔHf (CO) + 2ΔHf (H20)] – [ΔHf (CH3OH)] Experimental ∆Hf is “more” than theoretical because experimental heat of combustion is low (“inverse relationship”)
COMPLETE VS. INCOMPLETE COMBUSTION Characteristic Complete Combustion Incomplete Combustion Limiting Reagent Methanol Oxygen gas Formula CH3OH + 3/2O2 CO2 + 2H2O CH3OH + O2 CO + 2H2O Products Carbon dioxide gas Carbon monoxide gas (poisonous)
ADDRESSED PROBLEMS Assumption that total energy transferred to cork Bottle warm to the touch after reaction Insulation to reduce heat loss to environment Limiting reagent of reaction Volume of methanol used (0.4 mL)
CONCLUSION Energy not accounted for Energy escaped from bottle Multiple revisions to the procedure In the future… Made revision to get to where we are, in the future….blahblahblah -insulated container -low thermal conductivity
WORKS CITED Slide 3 – Fireworks. http://www.wallpaperdev.com/stock/fireworks-wallpapers-fireworks-bang-pics.jpg (accessed May 8, 2013). Slide 3 – Car Engine. http://www.yieldinsider.com/wp-content/uploads/2012/09/Car-Engine-1.jpg (accessed May 8, 2013). Slide 5 – Exothermic and Endothermic Reactions. http://chemistry.tutorvista.com/organic-chemistry/hammond-postulate.html (accessed May 8, 2013). Slide 7 – Methanol Structure. http://upload.wikimedia.org/wikipedia/commons/d/d1/Methanol_flat_structure.png (accessed May 8, 2013). Slide 7 – Methanol Ball-and-Stick Model. http://upload.wikimedia.org/wikipedia/commons/d/db/Methanol-3D-balls.png (accessed May 8, 2013).
TESLA COIL Tesla coils contain a transformer that changes low voltage to high voltage Increases the voltage and frequency When the electrode gets near another surface it discharges onto that surface
Incomplete Combustion Assumption: methanol would combust in complete combustion After experiment: methanol combusted in incomplete combustion Refer to Calculations XII & XIII in Appendix: Part 1