Excess Reactant Posted on 10th November 201527th July 2021 by ThePD (The Project Definition) An Excess Reactant is the reactant left over in a reaction that are not used up when the reaction is finished. Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in Technology and tagged chemistry, science. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.