Energy Release Calculation: Heptane vs Ethanol

How much energy is released during the complete combustion of 376 grams of heptane?

Assuming the same efficiency, would 376 grams of ethanol provide more, less, or the same amount of energy as 376 grams of heptane?

Energy Release Calculation:

To solve this problem, we first need to understand the energy release during the combustion of heptane and ethanol.

Heptane Energy Release:

The combustion of one mole of heptane, C7​H16​, releases 1.151×10^3 kcal of energy.

Calculation for 376 grams of Heptane:

Given that the molecular weight of heptane is approximately 100.21 g/mol, 376g of heptane is equivalent to about 3.75 moles.

Energy released by 376g of heptane: 1.151 × 10^3 kcal/mol × 3.75 mol = 4316.25 kcal

Ethanol Energy Release:

The combustion of one mole of ethanol, C2H5OH, typically releases about 326.7 kcal of energy.

Comparison:

Given that ethanol has a smaller molecular weight (~46.07 g/mol) compared to heptane, 376 grams of ethanol would provide more energy than the same amount of heptane.

Therefore, assuming the same efficiency, 376 grams of ethanol would produce more energy than heptane.

Explanation:

When comparing the energy release of heptane and ethanol, we consider their respective molecular weights and energy release per mole.

Heptane, with a higher molecular weight, releases more energy per mole compared to ethanol. However, due to the smaller molecular weight of ethanol, a larger quantity of ethanol (in this case, 376g) would provide a greater total energy release.

Therefore, 376 grams of ethanol would produce more energy than 376 grams of heptane, assuming the same efficiency of combustion.