How many grams of oxygen and gasoline must be burned by a car engine in order to generate 6831.5 J of energy which will be needed to pass a slow-moving tractor? When burning isooctane (gas) the formula is C8H18 and there are 5225.0 J produced per mole.

Expert Answers

An illustration of the letter 'A' in a speech bubbles

Here's the equation for the combustion of octane:

The moles of C8H18 needed to produce 6831.5 J of energy is:

(6831.5 J)(5225.0 J/mol) = 1.3075 moles

grams of C8H18 needed = (1.3075 mol)(115.0g/mol) = 150.4 g C8H18

Grams of O2 needed can be found from the mole ratio of O2 to C8H18 in the balanced equation, 11/2:

(1.3705 mol C8H18)(11 mol O2/2 mol C8H18)(32.0 g/mol) =

230.1 g O2 needed

This assumes complete combustion of octane. When insufficient oxygen is available hydrocarbons will combust incompletely, producing some CO and sometimes even C in place of some of the CO2.

The heat generated by burning octane in the cylinders of an internal combustion engine causes the exhaust gases to expand and exert pressure on the pistons in the cylinder. The pistons move up and down as gas is expanded and exhausted. This motion is transferred to the drive shaft which turns the wheels of the vehicle.

Approved by eNotes Editorial Team

We’ll help your grades soar

Start your 48-hour free trial and unlock all the summaries, Q&A, and analyses you need to get better grades now.

  • 30,000+ book summaries
  • 20% study tools discount
  • Ad-free content
  • PDF downloads
  • 300,000+ answers
  • 5-star customer support
Start your 48-Hour Free Trial