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
• Energy released
• ∆Hp < ∆Hr
• -∆Hrxn
Endothermic Reaction
• 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
Tesla Coil
Nalgene Bottle (500mL)
Methanol and Drierite
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
Mass
Specific Heat (Cp)
Air in Bottle
Bottle
Volume of bottle and Mass of bottle
density of air
(without copper
wires and insulation)
At the average
temperature of 300C
Temperature Change Thermometer
(∆T)
Specific heat of
LDPE
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
Limiting
Methanol
Reagent
Formula
CH3OH + 3/2O2 
CO2 + 2H2O
Incomplete
Combustion
Oxygen gas
Products
Carbon monoxide gas
(poisonous)
Carbon dioxide gas
CH3OH + O2  CO
+ 2H2O
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).