Yep basic chemistry kid, a reaction uses up all available materials, creating a new product, the gas...Go read a book.

There were no excess reagents because the reaction was fire, the fuel had no limiting reagent since the surrounding air offered plenty for the blaze. The reactant was used up in the reaction creating gas. Gas does not leaking the soil.

Use some common sense here.

Yep basic chemistry kid, a reaction uses up all available materials, creating a new product, the gas...Go read a book.