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```

## 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 ```