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).