If you are working in geoscience, you can apply chemical approach in different spheres.
1. Geochemistry - science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans or local systems like geochemistry of intrusions or destribution of minerals.
2 Biochemistry - the same thing, but in living organisms and you always need to connect your data to some area in 3d dimension.
In addition to Sergey's comments, water sources, their mapping and hydrology while in the realm of civil engineering may also be of interest to chemical engineers as well as tracking waste water from industries. If you have a chemical plant layout in say AutoCAD (3D) you can import that layer into ARC GIS and view the layout in real world space . GIS also has applications in mapping pollutant concentrations emitted by various chemical plants (COx, NOx, SOx, particulates, etc.). Point location of such pollutants may then be converted into kernel density that helps visualize concentrations of pollutants in large cities. I have similar maps in ARCGIS, a web mapping application
Chemical engineers develop alternative fuels and energy systems that allow our dependence on fossil fuels to be reduced. GIS is fundamentally the science of "where" things are. As long as what you seek to analyze in chemical engineering practice has a geographic index (i.e., XY Coordinates, Address), GIS can be used to locate or evaluate energy systems.
GIS can be used to any project with elements of spatial reference. There are many Chemical Engineering projects which are worked out in the field (not in the laboratory) and involve data collection in specific geographic locations (having spatial reference), then GIS could help you to manage such data (storage, retrieval) and provide you with unlimited number of tools for processing such data to derive useful information. This is the way they work most of the applications provided by yhe previous answers to your question.