In a reduction reaction why is it called reduction

Copper II oxide and magnesium oxide are both ionic compounds. If the above is written as an ionic equation, it becomes apparent that the oxide ions are spectator ions.

Omitting them gives:. In the above reaction, magnesium reduces the copper II ion by transferring electrons to the ion and neutralizing its charge.

Therefore, magnesium is a reducing agent. Another way of putting this is that the copper II ion is removing electrons from the magnesium to create a magnesium ion. The copper II ion is acting as an oxidizing agent. Confusion can result from trying to learn both the definitions of oxidation and reduction in terms of electron transfer and the definitions of oxidizing and reducing agents in the same terms. The following thought pattern can be helpful:.

Jim Clark Chemguide. Oxidation and reduction in terms of oxygen transfer The terms oxidation and reduction can be defined in terms of the adding or removing oxygen to a compound. Oxidation and Reduction with respect to Oxygen Transfer Oxidation is the gain of oxygen. Reduction is the loss of oxygen. Oxidation and reduction in terms of hydrogen transfer These are old definitions which are no longer used, except occasionally in organic chemistry. Oxidation and reduction can also be defined in terms of changes in composition.

The reverse is true for reduction : if a molecule loses oxygen atoms, the molecule is being reduced. Similarly, reduction and oxidation can be defined in terms of the gain or loss of hydrogen atoms. If a molecule adds hydrogen atoms, it is being reduced. If a molecule loses hydrogen atoms, the molecule is being oxidized.

Oxidation is the loss of electrons or the addition of oxygen; reduction is the gain of electrons or the addition of hydrogen. Chemical reactions in which electrons are transferred are called oxidation-reduction, or redox, reactions.

Oxidation is the loss of electrons. Reduction is the gain of electrons. Oxidation and reduction always occur together, even though they can be written as separate chemical equations.

Which reactions are redox reactions? For those that are redox reactions, identify the oxidizing and reducing agents. Balance each redox reaction by writing appropriate half reactions and combining them to cancel the electrons.

Learning Objectives To identify a chemical reaction as an oxidation-reduction reaction. To Your Health: Redox Reactions and Pacemaker Batteries All batteries use redox reactions to supply electricity because electricity is basically a stream of electrons being transferred from one substance to another.

Hydrogen is being removed from the original reactant molecule, so oxidation is occurring. Oxygen is being added to the original reactant molecule, so oxidation is occurring. Oxidation is occurring. Answer b: Oxygen is being removed. Reduction is occurring. Answer a: Hydrogen is being added. Concept Review Exercises Give two different definitions for oxidation and reduction. Answers Oxidation is the loss of electrons or the addition of oxygen; reduction is the gain of electrons or the addition of hydrogen.

At first, this might look like a simple decomposition reaction, because hydrogen peroxide breaks down to produce oxygen and water:. The key to this reaction lies in the oxidation states of oxygen, however. Notice that oxygen is present in the reactant and both products. In H 2 O 2 , oxygen has an oxidation state of In H 2 O, its oxidation state is -2, and it has been reduced. In O 2 however, its oxidation state is 0, and it has been oxidized.

Oxygen has been both oxidized and reduced in the reaction, making this a disproportionation reaction. The general form for this reaction is as follows:. Every balanced redox reaction is composed of two half-reactions: the oxidation half-reaction, and the reduction half-reaction.

For example, look at the following redox reaction between iron and copper:. In this reaction, iron is oxidized, and copper is reduced or, iron is the reducing agent , and copper is the oxidizing agent.

We can split this reaction into two half-reactions. The oxidation half-reaction looks as follows:. This shows the oxidation of iron and the loss of two electrons.

Notice that this equation is balanced in both mass and charge: we have one atom of iron on each side of the equation mass is balanced , and the net charge on each side of the equation is equal to zero charge is balanced. This half-reaction explicitly shows the copper II ion gaining two electrons. Note again that the equation is balanced in mass and charge. Now that we have our two balanced half-reactions, we can combine them to get the full redox reaction:. Adding the two halves of a redox reaction : These two halves of the reaction can be added like any other chemical equation.

Once the equations are added, the electrons on each side cancel out. Note that the two electrons on each side of the equation cancel out. This is very important, because the final balanced equation for any redox reaction should never contain any electrons. First, we need to split this reaction into its two half-reactions. We need to balance this equation by mass.

The equation is already balanced in nitrogens, but not oxygens. You can balance oxygen by adding the appropriate number of water molecules:. Now the equation is balanced in oxygens, but not hydrogens. The equation is now balanced in mass, but not charge. To balance the charge, we will add two electrons to the right side of the equation:. The equation is now balanced for mass, and we need only balance for charge. We therefore need to add 6 electrons to the right side of the equation to balance the charges:.

Lastly, in order to get our full balanced redox equation, we need to add our half-reactions so that all the electrons cancel out. For this reaction, we can multiply the first half-reaction by Although this example seems intimidating, balancing redox reactions in acidic solution becomes much easier with careful practice. For instance:. The half-reaction above is balanced for mass in acidic solution. If we are in basic solution, however, we would need to add 2 hydroxides to both sides of the equation:.

These species will neutralize each other to form water, so we can rewrite this as follows:. Lastly, because we have water molecules on both sides of the equation, we cancel out like terms to give us:.

This half-reaction is now balanced for mass in basic solution. From here, we proceed just as we did above in acidic solution: balance the charge by adding the appropriate number of electrons.