The combustion of octane will yield the most heat compared to glucose and ethanol.
The chemical oxidation/combustion reaction of glucose, octane, or ethanol will yield the most heat can be determined by comparing their respective enthalpy of combustion values. Enthalpy of combustion is the heat released when one mole of a substance undergoes complete combustion in excess oxygen. The substance with the highest enthalpy of combustion will release the most heat.
1. Glucose (C6H12O6):
Glucose is a carbohydrate and its combustion reaction is given by the equation:
C6H12O6 + 6O2 -> 6CO2 + 6H2O
2. Octane (C8H18):
Octane is an alkane and its combustion reaction is given by the equation:
2C8H18 + 25O2 -> 16CO2 + 18H2O
3. Ethanol (C2H5OH):
Ethanol is an alcohol and its combustion reaction is given by the equation:
C2H5OH + 3O2 -> 2CO2 + 3H2O
To determine which reaction will yield the most heat, we need to compare the enthalpy of combustion for each substance. The enthalpy of combustion values for glucose, octane, and ethanol are different, and the substance with the highest value will release the most heat.
Glucose: -2808 kJ/mol
Octane: -5471 kJ/mol
Ethanol: -1368 kJ/mol
Based on these values, octane has the highest enthalpy of combustion and will yield the most heat. It releases 5471 kJ of heat per mole of octane burned. In contrast, glucose releases 2808 kJ/mol, and ethanol releases 1368 kJ/mol.