Answer:
This means 463 grams of ethanol would provide less amount of energy
Explanation:
Step 1: Data given
Heat of combustion of ethanol = 326.7 kcal/mol
The heat of combustion of octane = 1.308*10³ kcal/mol
Mass of octane = 463 grams
Molar mass octane = 114.23 g/mol
Molar mass ethanol = 46.07 g/mol
Step 2: Calculate moles octane
Moles octane = mass octane / molar mass octane
Moles octane = 463 grams / 114.23 g/mol
Moles octane = 4.05 moles
Step 3: Calculate energy of combustion of 4.05 moles octane
Combustion of 1 mol octane gives us: 1.308 * 10³ kcal/mol
Combustion of 4.05 moles octane gives us 4.05 * 1.308 * 10³ kcal/mol = <u>5.30 * 10³ kcal</u>
This means the combustion reaction of 463 grams of octane gives us 5.30 * 10³ kcal
Step 4:
Heat of combustion of ethanol = 326.7 kcal/mol
OR in words: combustion of 1 mol ethanol gives us 326.7 kcal energy
Moles ethanol = 463 grams / 46.07 g/mol
Moles ethanol = 10.05 moles
Since combustion of 1 mol ethanol gives us 326.7 kcal
10.05 moles ethanol will give us = 10.05 * 326.7 = 3283.3 kcal = <u>3.28 * 10³ kcal</u>
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5.30 * 10³ kcal > 3.28 * 10³ kcal
This means 463 grams of ethanol would provide less amount of energy
