The enthalpy formation of ethanol, C2H5OH, is -277.0 kJ/mol @ 298.15 K. Calculate the enthalpy of combustion of one mole of ethanol, assuming that the products are CO2(g) & H2O (l).

C2H5OH + 3O2 ==> 2CO2 + 3H2O

deltaHrxn = (2*DHfCO2)+(3*DHfH2O)-(DHfC2H5OH = ??

32.5

To calculate the enthalpy of combustion of ethanol, we first need to understand the equation for the combustion reaction. The balanced chemical equation for the combustion of ethanol can be represented as follows:

C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l)

In this reaction, one mole of ethanol reacts with three moles of oxygen gas to produce two moles of carbon dioxide gas and three moles of water molecules.

To calculate the enthalpy of combustion, we need to use the given enthalpy of formation of ethanol and the enthalpies of formation of carbon dioxide and water. The enthalpy of formation is the change in enthalpy when one mole of a substance is formed from its constituent elements, with all reactants and products in their standard states.

Given values:
ΔHf⁰ (C2H5OH) = -277.0 kJ/mol (enthalpy of formation of ethanol)
ΔHf⁰ (CO2) = -393.5 kJ/mol (enthalpy of formation of carbon dioxide)
ΔHf⁰ (H2O) = -285.8 kJ/mol (enthalpy of formation of water)

The enthalpy of combustion (ΔHcombustion) can be calculated using the following equation:

ΔHcombustion = ΣnΔHf⁰(products) - ΣmΔHf⁰(reactants)

Where:
Σn is the sum of coefficients for the products
Σm is the sum of coefficients for the reactants
ΔHf⁰(products) and ΔHf⁰(reactants) are the enthalpies of formation of the respective products and reactants.

Using the given values and the equation, we can calculate the enthalpy of combustion of ethanol:

ΔHcombustion = [(2 × ΔHf⁰ (CO2)) + (3 × ΔHf⁰ (H2O))] - ΔHf⁰ (C2H5OH)

Substituting the given values:

ΔHcombustion = [(2 × -393.5 kJ/mol) + (3 × -285.8 kJ/mol)] - (-277.0 kJ/mol)

ΔHcombustion = [-787.0 kJ/mol + -857.4 kJ/mol] + 277.0 kJ/mol

ΔHcombustion = -1644.4 kJ/mol + 277.0 kJ/mol

ΔHcombustion = -1367.4 kJ/mol

Therefore, the enthalpy of combustion of one mole of ethanol is -1367.4 kJ/mol.

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