The complete combustion of ethanol, C 2 H 5 OH (FW = 46.0 g/mol ), proceeds as follows:
What is the enthalpy change for combustion of 15.0 g of ethanol?
To determine the enthalpy change for the combustion of ethanol, we need to use the balanced chemical equation and the enthalpy of combustion.
The balanced chemical equation for the combustion of ethanol is:
C2H5OH + 3O2 -> 2CO2 + 3H2O
From the equation, we can see that 1 mole of ethanol reacts with 3 moles of oxygen gas to produce 2 moles of carbon dioxide and 3 moles of water. The stoichiometric coefficients in the balanced equation indicate the molar ratios between the reactants and products.
To calculate the enthalpy change for the combustion reaction, we need to know the enthalpy of combustion of ethanol, which represents the heat released when 1 mole of ethanol is completely burned.
The enthalpy of combustion of ethanol is -1367.2 kJ/mol. The negative sign indicates that energy is released during the combustion process.
Step 1: Calculate the number of moles of ethanol in 15.0 g using its molar mass.
The molar mass of ethanol (C2H5OH) is 46.0 g/mol.
Number of moles = Mass / Molar mass
Number of moles = 15.0 g / 46.0 g/mol
Step 2: Calculate the enthalpy change for the combustion reaction using the number of moles of ethanol and the enthalpy of combustion.
Enthalpy change = Number of moles of ethanol x Enthalpy of combustion
Enthalpy change = (15.0 g / 46.0 g/mol) x (-1367.2 kJ/mol)
Simplifying the equation gives the enthalpy change for the combustion of 15.0 g of ethanol.