Calculate the number of pounds of CO2 released into the atmosphere when a 15.0-gallon tank of gasoline is burned in an automobile engine. Assume that gasoline is primarily octane, C8H18, and that the density of gasoline is 0.692 g·mL-1 (this assumption ignores additives). Also assume complete combustion.

266.997 pounds

Explanation:

The balanced equation for the combustion of octane is;

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

Assuming that gasoline is purely octane:

Amount of gasoline available is 15.0 gallon

We are required to calculate the amount of CO₂ released to the atmosphere;

This can be done in several steps;

Step 1: Mass of octane in grams

Amount of octane = 15.0 gallons

But, 1 gallon = 3785.41 ml

Therefore;

15 gallon is equivalent to;

= 15 * 3785.41 ml

= 56,781.15 ml

We are given the density of octane (0.692 g/ml) and thus we can calculate the mass of octane.

Mass = density * volume

= 0.692 g/ml * 56,781.15 ml

= 39,292.56 g

Step 2: Number of moles of octane

Number of moles = Mass / Molar mass

Molar mass of octane = 114.23 g/mol

Number of moles of Octane = 39,292.56 g : 114.23 g/mol

= 343.978 moles

Step 3: Moles of carbon dioxide released

From the equation;

2 moles of octane completely burns in air to yield 16 moles of CO₂

Therefore;

343.978 moles of octane produces;

= (343.978 moles/2) 16

= 2751.824 moles of CO₂

Step 4: Mass of CO₂ in pounds

1 mole of CO₂ has 44.01 g

Therefore;

2751.824 moles contains;

= 2751.824 moles * 44.01 g/mol

= 121,107.77 g

But, 1 pound = 453.592 g

Therefore;

Mass of CO₂ in pounds = 121,107.77 g : 453.592 g

= 266.997 pounds

Therefore, the mass of CO₂ released to the atmosphere is 266.997 pounds