Question

Ethanol, C2H6O, is most often blended with gasoline - usually as a 10 per cent mix - to create a fuel called gasohol. Ethanol is a renewable resource and ethanol-blended fuels, like gasohol, appear to burn more efficiently in combustion engines. The heat of combustion of ethanol is 326.7 kcal/mol.

The heat of combustion of 2-methylheptane, C8H18, is 1.306×103 kcal/mol. How much energy is released during the complete combustion of 394 grams of 2-methylheptane ?
_______kcal
Assuming the same efficiency, would 394 grams of ethanol provide more, less, or the same amount of energy as 394 grams of 2-methylheptane?
_________
A. more or
B. less or
C. the same amount

Answer 1

Answer: the answer is B. less

Step-by-step explanation:

hope this helps :D

Answer 2

4.51 × 10³ kcal

B. less

Step-by-step explanation:

Let's consider the combustion of 2-methylheptane.

C₈H₁₈ + 12.5 O₂ ⇒ 8 CO₂ + 9 H₂O

When 1 mole of C₈H₁₈ burns, 1.306 × 10³ Kcal are released (heat of combustion). The molar mass of C₈H₁₈ is 114 g/mol. Then, for 394 g of C₈H₁₈:

`394gC_(8)H_(18).(1molC_(8)H_(18))/(114gC_(8)H_(18)).(1.306 * 10^(3) kcal )/(1molC_(8)H_(18))  =4.51 * 10^(3) kcal`

Assuming the same efficiency, would 394 grams of ethanol provide more, less, or the same amount of energy as 394 grams of 2-methylheptane?

Let's consider the combustion of ethanol.

C₂H₆O + 3 O₂ ⇒ 2 CO₂ + 3 H₂O

When 1 mole of C₂H₆O burns, 326.7 Kcal are released (heat of combustion). The molar mass of C₂H₆O is 46.0 g/mol. Then, for 394 g of C₂H₆O:

`394gC_(2)H_(6)O.(1molC_(2)H_(6)O)/(46.0gC_(2)H_(6)O).(326.7 kcal )/(1molC_(2)H_(6)O)  =2.80 * 10^(3) kcal`

The combustion of 394 g of ethanol provides less energy than the combustion of 394 g of 2-methylheptane.