MATLAB Examples

zHW: Complete Combustion of Octane

Find the balanced reaction for the complete combuston of octane to carbon dioxide and water.

Octane

          H   H   H   H   H   H   H   H
          |   |   |   |   |   |   |   |
      H - C - C - C - C - C - C - C - C - H
          |   |   |   |   |   |   |   |
          H   H   H   H   H   H   H   H

Contents

Chemical Formulas

Four species participate in the combustion reaction: octane, oxygen, carbon dioxide, and water. The first step is to construct a cell array with the formula for these species. Displaying the molecular weights is a convenient way to verify that the formulas are correctly entered.

species = {'CH3(CH2)6CH3','O2','CO2','H2O'};
molweight(species);
Species                    Mol. Wt.
-------                    --------
CH3(CH2)6CH3                 114.23
O2                            32.00
CO2                           44.01
H2O                           18.02

Stoichiometric Coefficients

Stoichiometric coefficients for the balanced reaction (or balanced reactions, if more than one independent reaction is possible) is computed with stoich. Reactants have a negative stoichiometric coefficient, products have positive coefficients.

V = stoich(species);
disp(' ');
disp('Stoichiometric Matrix V = ');
disp(V);
 
Stoichiometric Matrix V = 
   -1.0000
  -12.5000
    8.0000
    9.0000

Display Balanced Reactions

The balanced reaction displayed as follows. Notice that stoichiometric coefficients are converted to integers for the displayed reaction. The balanced reaction is displayed in several different notations.

disp_reaction(V,species);
disp_reaction(V,hillformula(species));
disp_reaction(V,{'Octane','Oxygen','Carbon Dioxide','Water'});
2 CH3(CH2)6CH3 + 25 O2 <=> 16 CO2 + 18 H2O


2 C8H18 + 25 O2 <=> 16 CO2 + 18 H2O


2 Octane + 25 Oxygen <=> 16 Carbon Dioxide + 18 Water