science
Combustion of Alcohols
Purpose: The purpose of this investigation is to use calorimetry to determine the molar enthalpy change in the combustion of each of a series of alcohols.
Question: How do the enthalpies of combustion change as the alcohol molecules become larger?
Prediction: I predict the bigger the molecule the more the energy will be released.
Materials: On lab sheet
Procedure: On lab sheet
Observation: On other page
Analysis: b) i) Ethanol – q=(100g)(4.18J/g/C)(25.5C) q=10659J Propanol – q=(100g)(4.18J/g/C)(21.5C) q=8987J Butanol – q=(100g)(4.18J/g/C)(23.5C) q=9823J ii) Ethanol – 10659J/0.985g= 10.8kJ/g
Propanol – 8987J/0.845g= 10.6kJ/g
Butanol – 9823J/0.75g = 13.1 kJ/g iii) Ethanol – n=0.985g/46.01g/mol = 0.0214 mol
Propanol – n=0.845g/60.01g/mol = 0.0141 mol
Butanol – n=0.75g/74.1g/mol = 0.0101 mol iv) Propanol – 8987J/0.0141 mol = 637kJ/mol
Ethanol – 10659J/0.0214 mol = 498kJ/mol
Butanol – 9823J/0.0101mol = 973kJ/mol
c) Ethanol
C2H6O + 2O2 ->2CO2 +3H2O + 498kJ
C2H6O + 2O2 ->2CO2 +3H2O ΔH=498kJ
Propanol
2C3H8 O + 9O2 -> 6CO2 + 8H2O + 637kJ
2C3H8 O + 9O2 -> 6CO2 + 8H2O ΔH=637kJ
Butanol
2C4H10O + 12O2 -> 8CO2 + 10H2O + 973kJ
2C4H10O + 12O2 -> 8CO2 + 10H2O ΔH=973kJ
d) According to the measured data, as the alcohol molecules become larger, the enthalpies of the combustion become larger too therefore, the bigger the molecule, the more energy is released. The prediction I made was correct.
e) Sources of experimental error in this experiment can be if you didn’t measure the alcohol right after it was burned. If you spilled any alcohol. If you didn’t record the temperature after you put out the fire.
f) Ethanol 498kJ/mol / 1369kJ/mol = 36%
Propanol 637kJ/mol / 2008kJ/mol = 32%
Butanol 973kJ/mol / 3318 kJ/mol = 29%
The Experimental Design is not an acceptable method to answer the question because the values are only 32% of the accepted values.
g) Butanol, because it uses less alcohol per gram
Purpose: The purpose of this investigation is to use calorimetry to determine the molar enthalpy change in the combustion of each of a series of alcohols.
Question: How do the enthalpies of combustion change as the alcohol molecules become larger?
Prediction: I predict the bigger the molecule the more the energy will be released.
Materials: On lab sheet
Procedure: On lab sheet
Observation: On other page
Analysis: b) i) Ethanol – q=(100g)(4.18J/g/C)(25.5C) q=10659J Propanol – q=(100g)(4.18J/g/C)(21.5C) q=8987J Butanol – q=(100g)(4.18J/g/C)(23.5C) q=9823J ii) Ethanol – 10659J/0.985g= 10.8kJ/g
Propanol – 8987J/0.845g= 10.6kJ/g
Butanol – 9823J/0.75g = 13.1 kJ/g iii) Ethanol – n=0.985g/46.01g/mol = 0.0214 mol
Propanol – n=0.845g/60.01g/mol = 0.0141 mol
Butanol – n=0.75g/74.1g/mol = 0.0101 mol iv) Propanol – 8987J/0.0141 mol = 637kJ/mol
Ethanol – 10659J/0.0214 mol = 498kJ/mol
Butanol – 9823J/0.0101mol = 973kJ/mol
c) Ethanol
C2H6O + 2O2 ->2CO2 +3H2O + 498kJ
C2H6O + 2O2 ->2CO2 +3H2O ΔH=498kJ
Propanol
2C3H8 O + 9O2 -> 6CO2 + 8H2O + 637kJ
2C3H8 O + 9O2 -> 6CO2 + 8H2O ΔH=637kJ
Butanol
2C4H10O + 12O2 -> 8CO2 + 10H2O + 973kJ
2C4H10O + 12O2 -> 8CO2 + 10H2O ΔH=973kJ
d) According to the measured data, as the alcohol molecules become larger, the enthalpies of the combustion become larger too therefore, the bigger the molecule, the more energy is released. The prediction I made was correct.
e) Sources of experimental error in this experiment can be if you didn’t measure the alcohol right after it was burned. If you spilled any alcohol. If you didn’t record the temperature after you put out the fire.
f) Ethanol 498kJ/mol / 1369kJ/mol = 36%
Propanol 637kJ/mol / 2008kJ/mol = 32%
Butanol 973kJ/mol / 3318 kJ/mol = 29%
The Experimental Design is not an acceptable method to answer the question because the values are only 32% of the accepted values.
g) Butanol, because it uses less alcohol per gram