Concept explainers
Ethanol
Interpretation:
The price of ethanol is to be calculated.
Concept introduction:
The standard enthalpy for a reaction is the amount of enthalpy that occurs under standard conditions.
The standard enthalpy of reaction is determined by using the equation given below:
Here, the stoichiometric coefficients are represented by m for the reactants and n for the products and the enthalpy of formation under standard conditions is represented by
The value of the enthalpy of formation of an element is zero at its most stable state.
Answer to Problem 83AP
Solution:
Explanation of Solution
Given information: Density
Density
The combustion of octane takes place as follows:
From appendix 2,
The oxygen gas is in its most stable form, so its enthalpy of formation is zero.
Calculate the standard enthalpy of the reaction for the combustion of octane as follows:
Substitute
for
in the above equation
Convert kilojoule per mole to kilojoule per gallon as follows:
The combustion of ethanol takes place as follows:
From appendix 2,
Calculate the standard enthalpy of the reaction for the combustion of ethanol as follows:
Substitute
for
Convert kilojoule per mole to kilojoule per gallon as follows:
Now, the cost of ethanol per gallon is
The price of ethanol is
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