Material balances for combustion of octane

One of the most common chemical reactors found around us is the car
engine. It takes gasoline and reacts it with air to release chemical
energy, which in turn is transformed into mechanical energy. Emissions
from your car’s engine have been an environmental concern for many
years.

Using the concepts of material balances, determine how much (in moles
and lbs) air is needed and CO2, N2, CO, and H2O are emitted for every
gallon of gasoline burned in your car’s engine. Assume that gasoline,
a mixture of many hydrocarbons, can be modeled as pure octane (C8H18).
Assume that 90% of the octane is turned into carbon dioxide and water,
and 10% of the octane is turned into carbon monoxide and water. No
excess air is involved in the reaction, meaning only enough air to
provide the needed oxygen is introduced into the engine. Also assume
the nitrogen in the air does not react at the temperature of your
engine. Use the variables nO2, nN2, nCO, nCO2, nN2, and nH2O to
represent the number of moles of each component in various streams.

C8H18 + O2 ( CO2 + CO+ H2O



Gasoline

1 gallon

Car Engine

Air

21 mol% O2; nO2

79 mol% N2; nN2

Emissions

nCO, nCO2, nH2O, nN2