Chem edapt wk 5
Introduction
Reduction and oxidation are intertwined concepts that are
important to understanding some of the most important
chemical reactions in the human body. In this lesson, we will
explore the relationship between these terms and the how to
identify what chemicals in a reduction/oxidation reaction
(redox reaction) are playing which parts.
QUESTION:
If iron reacts with oxygen gas in the reaction 2 Fe(s) +
O2(g)
→ 2 FeO(s), what is oxidized in this reaction?
In a redox reaction, the atom being oxidized often accepts
an oxygen atom. Iron is oxidized in this reaction as the Fe is
joined to an oxygen.
Reduction and Oxidation
Reduction and oxidation involves the transfer of
electrons between two species within a chemical reaction.
Not all chemical reactions involve reduction and oxidation;
however, the reactions that involve reduction and oxidation
are called Redox reactions. As usual, we need to understand
a bit of terminology in order to understand these reactions
further.
• Oxidation: loss of electrons
• Reduction: gain of electrons
You may find the word “reduction” a bit of an odd choice for a
reaction that involves gaining of electrons. The key is to
remember that electrons have a -1 charge, and thus, the
more electrons an atom gains, the more negative the charge.
To help remember these terms, the mnemonic below can
help:
LEO the lion goes GER: Loss of Electrons is Oxidation and
Gain of Electrons is Reduction
,In a chemical reaction, oxidation cannot happen without
reduction and reduction cannot happen without oxidation.
Question: Oxidation involves the loss of electrons while
reduction involves the gain of electrons. Consider a reaction
where a Li+ is converted into Li. Do you think that this Lithium
atom gained or lost an electron?
gained electron.
lost electron
Ion to Neutral Atom Conversion
In this specific case, a lithium ion (Li+) has a positive charge due to the loss
of one electron. When this ion is transformed into a neutral lithium atom (Li),
it must gain an electron to neutralize its positive charge. Thus, the
conversion from Li+ to Li represents a reduction process because the lithium
ion gains an electron.
Summary
Therefore, in the reaction where Li+ is converted into Li, the lithium atom
gained an electron.
Identifying Oxidation and
Reduction
We know that electrons have a -1 charge, and we understand that
+1 -1 = 0. So, if Li+ gains an electron, this is what cancels
out the positive (+1) charge and makes this atom neutral.
The rule for oxidation and reduction, based on the gain or loss
of electrons is that:
• As the charge of a species increases in the positive
direction, the species is oxidized.
• As the charge of a species decreases, becoming
more negative, the species is reduced.
,A visualization of this relationship appears in the image. Note
the direction of the arrows. When the Li+ became Li, we see
that we moved from +1 to 0, or downwards, telling us that
this process was reduction.
As we see, if charges are present, determining reduction and
oxidation is as easy as looking at how the charges change.
, Conclusion
In the specified reactions, we can determine whether the species is oxidized
or reduced based on the changes in their oxidation states. The oxidation
state changes help to identify the electron transfer that occurs during the
reactions. Below is a detailed explanation for each reaction.
1. Mg²⁺ Becomes Mg
When magnesium ion (Mg²⁺) is converted to magnesium metal (Mg), it gains
two electrons:
Mg2++2e−→Mg
In this process, Mg²⁺ is reduced.
2. O Becomes O²⁻
When oxygen (O) is converted to oxide ion (O²⁻), it gains two
electrons: O+2e−→O2−
This indicates that oxygen is reduced.
3. Fe²⁺ Becomes Fe³⁺
In this transformation, iron (Fe²⁺) loses one electron to become
iron (Fe³⁺): Fe2+→Fe3++e−
Here, Fe²⁺ is oxidized.
Introduction
Reduction and oxidation are intertwined concepts that are
important to understanding some of the most important
chemical reactions in the human body. In this lesson, we will
explore the relationship between these terms and the how to
identify what chemicals in a reduction/oxidation reaction
(redox reaction) are playing which parts.
QUESTION:
If iron reacts with oxygen gas in the reaction 2 Fe(s) +
O2(g)
→ 2 FeO(s), what is oxidized in this reaction?
In a redox reaction, the atom being oxidized often accepts
an oxygen atom. Iron is oxidized in this reaction as the Fe is
joined to an oxygen.
Reduction and Oxidation
Reduction and oxidation involves the transfer of
electrons between two species within a chemical reaction.
Not all chemical reactions involve reduction and oxidation;
however, the reactions that involve reduction and oxidation
are called Redox reactions. As usual, we need to understand
a bit of terminology in order to understand these reactions
further.
• Oxidation: loss of electrons
• Reduction: gain of electrons
You may find the word “reduction” a bit of an odd choice for a
reaction that involves gaining of electrons. The key is to
remember that electrons have a -1 charge, and thus, the
more electrons an atom gains, the more negative the charge.
To help remember these terms, the mnemonic below can
help:
LEO the lion goes GER: Loss of Electrons is Oxidation and
Gain of Electrons is Reduction
,In a chemical reaction, oxidation cannot happen without
reduction and reduction cannot happen without oxidation.
Question: Oxidation involves the loss of electrons while
reduction involves the gain of electrons. Consider a reaction
where a Li+ is converted into Li. Do you think that this Lithium
atom gained or lost an electron?
gained electron.
lost electron
Ion to Neutral Atom Conversion
In this specific case, a lithium ion (Li+) has a positive charge due to the loss
of one electron. When this ion is transformed into a neutral lithium atom (Li),
it must gain an electron to neutralize its positive charge. Thus, the
conversion from Li+ to Li represents a reduction process because the lithium
ion gains an electron.
Summary
Therefore, in the reaction where Li+ is converted into Li, the lithium atom
gained an electron.
Identifying Oxidation and
Reduction
We know that electrons have a -1 charge, and we understand that
+1 -1 = 0. So, if Li+ gains an electron, this is what cancels
out the positive (+1) charge and makes this atom neutral.
The rule for oxidation and reduction, based on the gain or loss
of electrons is that:
• As the charge of a species increases in the positive
direction, the species is oxidized.
• As the charge of a species decreases, becoming
more negative, the species is reduced.
,A visualization of this relationship appears in the image. Note
the direction of the arrows. When the Li+ became Li, we see
that we moved from +1 to 0, or downwards, telling us that
this process was reduction.
As we see, if charges are present, determining reduction and
oxidation is as easy as looking at how the charges change.
, Conclusion
In the specified reactions, we can determine whether the species is oxidized
or reduced based on the changes in their oxidation states. The oxidation
state changes help to identify the electron transfer that occurs during the
reactions. Below is a detailed explanation for each reaction.
1. Mg²⁺ Becomes Mg
When magnesium ion (Mg²⁺) is converted to magnesium metal (Mg), it gains
two electrons:
Mg2++2e−→Mg
In this process, Mg²⁺ is reduced.
2. O Becomes O²⁻
When oxygen (O) is converted to oxide ion (O²⁻), it gains two
electrons: O+2e−→O2−
This indicates that oxygen is reduced.
3. Fe²⁺ Becomes Fe³⁺
In this transformation, iron (Fe²⁺) loses one electron to become
iron (Fe³⁺): Fe2+→Fe3++e−
Here, Fe²⁺ is oxidized.
