Determination of amount of ascorbic acid in a vitamin C tablet by redox titration

Oxidation is a chemical change involving the loss of electrons that results in an increased oxidation number. This process also includes the loss of a hydrogen atom or gain of an oxygen atom. An example of oxidation is solid zinc losing electrons to go into its ionized form:

Reduction is the exact opposite of oxidation. It involves a gain of electrons resulting in decreased or reduced oxidation number. Reduction may involve gaining a hydrogen atom or losing an oxygen atom. Aqueous copper gaining electrons to go into its solid form is an example of reduction.