Question

1. The combustion of gasoline in a car is similar to our respiration of C₁₂H₂₂O₁₁(s) sugar/food where the products for both are carbon dioxide and water. The complete balance equations for the combustion of gasoline and sugar are listed below

2 C₈H₁₈ (l) + 25 O₂ (g) → 16 CO₂ (g) + 18 H₂O (g)

C₁₂H₂₂O₁₁(s) + 12 O₂ (g) → 12 CO₂ (g) + 11 H₂O (g)

1. How much energy (in kJ) is produced by the combustion of 1.60 gallons of gasoline?

How much energy (in kJ) is produced by the combustion of 10.0 pounds of sugar?

Standard heats for reaction (combustion): ΔH Gasoline = -5470 kJ/mole; ΔH Sugar = -5646 kJ/mole

Formula for gasoline is C₈H₁₈ and has a density of 0.75 g/mL; 1L = 0.26417 gal

Formula for sugar is C₁₂H₂₂O₁₁ ; 1 g = 0.0022 lb

1. Which reaction produces more energy, burning 1.6 gal of gasoline or eating 10 lb of sugar?

1. One serving of Doritos, 28g, contains 150 kcal of energy. Calculate the calories per g for Doritos and compare the answer to sucrose: 3.728 kcal/g. Which is better if your trapped in the wilderness?

Answer 1

1.

Given that

2 C8H18 (l) + 25 O2 (g) → 16 CO2 (g) + 18 H2O (g)

C12H22O11(s) + 12 O2 (g) → 12 CO2 (g) + 11 H2O (g)

Standard heats for reaction (combustion): ΔH Gasoline = -5470 kJ/mole; ΔH Sugar = -5646 kJ/mole

1.60 gallons of gasoline

Density = mass/ volume

Mass = density * volume

density of 0.75 g/mL; 1L = 0.26417 gal

1.60 gallons of gasoline = 6.05666 L

Or 6056.66 ml

Mass of gasoline = 0.75 g/mL*6056.66 ml

=4542.495 g

Number of moles = amount in g / molar mass

= 4542.495 g/114.232 g·mol−1

= 39.77 moles

Energy produced= ΔH Gasoline * number of moles

= -5470 kJ/mole *39.77 moles

= -217541.9 KJ

10.0 pounds of sugar or 4535.92 g

Moles of sugar = 4535.92 g/342.3 g/mol

= 13.25 moles

Energy produced= ΔH Sugar * number of moles

= -5646 kJ/mole*13.25 moles

= - 74809.5 KJ

burning 1.6 gal of gasoline reaction produces more energy