Video Transcript
Which of the following is a
substrate that is oxidized? (A) Cationic species, (B) anionic
species, (C) neutral species, (D) reducing agent, (E) oxidizing agent.
This question is asking us to
identify which of the following substrates or chemical species is being
oxidized. In order to answer this problem,
let us first discuss oxidation, which is a chemical reaction where a chemical
species loses electrons. This means that a substrate that is
oxidized will be able to lose electrons during a reaction. Since the oxidized substrate will
give electrons to the other species, the number of electrons within the oxidized
species will reduce. Therefore, we can also refer to the
oxidized species as the reducing agent.
A reducing agent is a chemical
species that reduces another chemical species while being oxidized itself. For example, let us take a look at
the following reaction, when sodium reacts with chlorine gas to produce sodium
chloride. When looking at elemental sodium on
the reactant side, it has an oxidation number of zero. And the sodium ion on the product
side in NaCl has an oxidation number of one plus. Therefore, sodium is being oxidized
and would be the reducing agent since one electron is being lost.
In a redox reaction, besides
oxidation, there must be reduction, which is a chemical reaction where a chemical
species gains electrons. This means that a substrate that is
reduced will be able to gain electrons during a reaction. Since the reduced substrate will
gain electrons to the other species, the number of electrons within the reduced
species will increase. Therefore, we can also refer to the
reduced species as the oxidizing agent.
The oxidizing agent is a chemical
species that oxidizes another chemical species while being reduced itself. In this example, elemental chlorine
has an oxidation number of zero on the reactant side. And the chloride ion on the product
side has an oxidation number of one minus. Therefore, chlorine is being
reduced, since electrons are gained, and is classified as the oxidizing agent.
On a side note, let us not forget
to balance the oxidation and reduction reaction to demonstrate a loss of two
electrons from sodium and a gain of two electrons for chlorine.
When looking at the answer choices,
the correct answer is letter (D). A substrate that is oxidized is
called the reducing agent.
