Redox Reaction
Oxidation-Reduction Reaction
What is a Redox Reaction?
A redox reaction is a chemical reaction in which the atoms change their oxidation numbers. Some atoms lose electrons and are oxidized – a process known as oxidation. On the other hand, some atoms gain electrons and are reduced – a process known as reduction. Therefore, both REDuction and OXidation take place simultaneously, hence the term redox. Redox reactions usually occur in one of two environments: acidic or basic
Identifying Redox Reactions
A way to recognize a redox reaction is to look for a change in the oxidation number of the two elements involved in the reaction. The oxidized element increases its oxidation number, while the reduced element decreases its oxidation number. By checking this change, one can quickly determine and tell whether the reaction is redox or not.
What Happens in a Redox Reaction?
In a redox reaction, electrons move from one atom to another, which changes the oxidation number or state of the two atoms. The oxidation state of an element corresponds to the number of electrons an atom loses, gains, or appears to use when combining with other atoms in compounds.
Redox Half-Reaction
A half-reaction is the part of an overall reaction that separately represents either an oxidation or a reduction. Two half-reactions, including one oxidation and one reduction, must describe a redox reaction completely [4].
Example
When a nickel (Ni) strip is placed in an aqueous solution of copper (II) sulfate (CuSO4), an immediate reaction occurs. Copper metal begins to deposit on the strip. The only source of metallic copper in this system is the copper (II) ions (Cu^2+) in the solution. The reaction is represented as follows.
Cu^2+ + 2e– → Cu(0) Here, the Cu^2+ ion gains two electrons and is reduced to Cu (0). So, the above equation represents the reduction part of a redox reaction, and hence, it is called a redox half-reaction.
On the other hand, nickel releases two electrons to form nickel (II) ions (Ni2+). These are the two electrons that go to copper.
Ni → Ni^2+ + 2e–
Thus, nickel is oxidized, and the above half-reaction represents the oxidation part of the redox reaction.
Balancing Redox Reaction using Half-Reaction
The half-reaction can be used to balance the redox reaction. Consider an example of the combustion redox reaction between magnesium (Mg) and oxygen (O2), resulting in magnesium oxide (MgO). The unbalanced equation is given by:
Mg (s) + O2 (g) → MgO (s)
Mg loses two electrons and becomes an Mg^2+ cation. Its oxidation number goes from zero to +2. Hence, it is oxidized. The oxidation part of the reaction is written as:
Mg (s) → Mg^2+ + 2 e–
On the other hand, O gains two electrons from Mg and becomes O^2-, thereby changing its oxidation number from zero to -2. Hence, oxygen is reduced, and the reduction part of the reaction is: ½ O2 (g) + 2 e– → O^2- Adding the two equations together: Mg (s) + ½ O2 (g) → MgO (s) Multiplying both sides by 2: 2 Mg (s) + O2 (g) → 2 MgO (s)
Examples of Redox Reaction
Redox equation
Pedro Mejia Mendoza
Created on February 1, 2023
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Transcript
Redox Reaction
Oxidation-Reduction Reaction
What is a Redox Reaction?
A redox reaction is a chemical reaction in which the atoms change their oxidation numbers. Some atoms lose electrons and are oxidized – a process known as oxidation. On the other hand, some atoms gain electrons and are reduced – a process known as reduction. Therefore, both REDuction and OXidation take place simultaneously, hence the term redox. Redox reactions usually occur in one of two environments: acidic or basic
Identifying Redox Reactions
A way to recognize a redox reaction is to look for a change in the oxidation number of the two elements involved in the reaction. The oxidized element increases its oxidation number, while the reduced element decreases its oxidation number. By checking this change, one can quickly determine and tell whether the reaction is redox or not.
What Happens in a Redox Reaction?
In a redox reaction, electrons move from one atom to another, which changes the oxidation number or state of the two atoms. The oxidation state of an element corresponds to the number of electrons an atom loses, gains, or appears to use when combining with other atoms in compounds.
Redox Half-Reaction
A half-reaction is the part of an overall reaction that separately represents either an oxidation or a reduction. Two half-reactions, including one oxidation and one reduction, must describe a redox reaction completely [4]. Example When a nickel (Ni) strip is placed in an aqueous solution of copper (II) sulfate (CuSO4), an immediate reaction occurs. Copper metal begins to deposit on the strip. The only source of metallic copper in this system is the copper (II) ions (Cu^2+) in the solution. The reaction is represented as follows. Cu^2+ + 2e– → Cu(0) Here, the Cu^2+ ion gains two electrons and is reduced to Cu (0). So, the above equation represents the reduction part of a redox reaction, and hence, it is called a redox half-reaction. On the other hand, nickel releases two electrons to form nickel (II) ions (Ni2+). These are the two electrons that go to copper. Ni → Ni^2+ + 2e– Thus, nickel is oxidized, and the above half-reaction represents the oxidation part of the redox reaction.
Balancing Redox Reaction using Half-Reaction
The half-reaction can be used to balance the redox reaction. Consider an example of the combustion redox reaction between magnesium (Mg) and oxygen (O2), resulting in magnesium oxide (MgO). The unbalanced equation is given by: Mg (s) + O2 (g) → MgO (s) Mg loses two electrons and becomes an Mg^2+ cation. Its oxidation number goes from zero to +2. Hence, it is oxidized. The oxidation part of the reaction is written as: Mg (s) → Mg^2+ + 2 e–
On the other hand, O gains two electrons from Mg and becomes O^2-, thereby changing its oxidation number from zero to -2. Hence, oxygen is reduced, and the reduction part of the reaction is: ½ O2 (g) + 2 e– → O^2- Adding the two equations together: Mg (s) + ½ O2 (g) → MgO (s) Multiplying both sides by 2: 2 Mg (s) + O2 (g) → 2 MgO (s)
Examples of Redox Reaction