Post on 11-Dec-2015
ENTHALPY OF FORMATION:Combustion of Methanol
River Dell High School
Team AJason 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– ∆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
EXPERIMENT APPARATUS
• Stopper – with green line• Methanol (stored in Drierite) • Nalgene bottle (500 mL)• Insulation– Bubble wrap– Glass fiber
• Tesla coil– Copper wires
EXPERIMENT APPARATUS
Rubber Stopper
Methanol and DrieriteNalgene Bottle (500mL)
Tesla Coil
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)
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)]
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…
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).