Answer
This reaction is oxidation because the fumarate molecule has lost two electrons as shown by the loss of two hydrogen atoms in the chemical makeup of the molecule.
OIL-RIG (Oxidation Is Losing - Reduction Is Gaining). Losing/Gaining refers to electrons. You can see the loss or gain of electrons by tracing the H-atoms. If there are less H-atoms in the product molecule, this means you have lost electrons because an H-atom contains one electron. If there are more H-atoms in the product molecule, this means you have gained electrons because an H-atom contains one electron.
Work Step by Step
See answer above.
