The general chemical equation for the combustion of fossil fuels, such as coal, natural gas, and petroleum, is:

```

C<sub>x</sub>H<sub>y</sub> + O<sub>2</sub> -> CO<sub>2</sub> + H<sub>2</sub>O + energy

```

In this equation, "C_xH_y" represents the hydrocarbon fuel, where "x" and "y" are integers that indicate the number of carbon and hydrogen atoms in the fuel molecule. "O₂" represents oxygen gas from the air, which reacts with the fuel during combustion. The products of combustion are carbon dioxide (CO₂) and water vapor (H₂O), along with the release of energy in the form of heat and light.