Regent’s Warm-Up
What is the electron configuration
of a sulfur atom in the ground
state?
(1) 2–4
(2) 2–6
(3) 2–8–4
(4) 2–8–6
Regent’s Warm-Up
What is the electron configuration
of a sulfur atom in the ground
state?
(1) 2–4
(2) 2–6
(3) 2–8–4
(4) 2–8–6
Oxidation Reduction Reactions
s
AIM:
What are OxidationReduction Reactions?
Do Now:
If the conc. Of a product is
increased how will the
equilibrium state be
affected?
Oxidation Reduction Reactions
What are they used for? Why are they important?…
• Purifying metals
• Protecting metals
(e.g. Al, Na, Li)
from corrosion
• Balancing complex
• Producing gases
chemical equations
(e.g. Cl2, O2, H2)
• Sensors and
• Electroplating
machines (e.g. pH
metals
meter)
• Electrical production
(batteries, fuel cells)
Oxidation Reduction Reactions
Classical Definitions
• Oxidation – the combination of a substance
with oxygen
Example:
2Mg(s) + O2(g)  2MgO(s)
• O2 is the OXIDIZING AGENT
• Mg gains oxygen and is oxidized
Oxidation Reduction Reactions
Classical Definitions
• Reduction – the removal of O2 from a
substance
Example:
CuO(aq) + H2(g)  Cu(s) + H2O(l)
• H2 is the REDUCING AGENT
• CuO loses oxygen and is reduced
Oxidation Reduction Reactions
Current Definitions
Take into account the charge of the ions and
atoms involved in the reaction
• Oxidation – the Loss of Electrons
Example:
2Mg0 + O20  2Mg+2O-2
• The oxidation # of Mg goes from 0 to +2
-
• Since Mg0 lost 2e s, Mg0 is OXIDIZED
0
+2
2Mg  2Mg + 4e
Oxidation Reduction Reactions
Current Definitions
• Reduction – the Gain of Electrons
Example: Cu+2O-2 + H20  Cu0 + H2+1O-2
• If you look closely oxygen is not reacting, its
oxidation # stays the same (-2)
• Copper goes from Cu+2 to Cu0
• Copper gains 2e s & is REDUCED
-
Cu + 2e s  Cu0
+2
Oxidation Reduction Reactions
What is the MAIN
difference between the
classical and current
definitions?
*Oxygen is NOT
required in the current
definition*
• Which particles are
gained and lost during
a redox reaction?
(1) electrons
(2) protons
(3) neutrons
(4) positrons
Oxidation Reduction Reactions
• Oxidation and Reduction
reactions are opposite
processes that occur
simultaneously
In a redox reaction, how does the total
number of electrons lost by the oxidized
substance compare to the total number
of electrons gained by the reduced
substance?
• For something to lose an
electron there must be
something else that wants
to gain that electron
1. The number lost is always greater
than the number gained.
2. The number lost is sometimes equal
to the number gained.
3. The number lost is always equal to
the number gained.
4. The number lost is sometimes less
than the number gained.
Oxidation Reduction Reactions
• Loss of Electrons is
Oxidation
• Gain of Electrons is
Reduction
• LEO the lion says GER
Oxidation Reduction Reactions
• The substance that
loses electrons is
OXIDIZED and is the
REDUCING AGENT
• The substance that
gains electrons is
REDUCED and is the
OXIDIZING AGENT
In any redox reaction, the
substance that undergoes
reduction will
1. lose electrons and have a
decrease in oxidation number
2. gain electrons and have a
decrease in oxidation number
3. lose electrons and have an
increase in oxidation number
4. gain electrons and have an
increase in oxidation number
Oxidation Reduction Reactions
Which half-reaction
Given the balanced ionic equation
representing a reaction:
correctly represents
reduction?
2Al3+(aq) + 3Mg(s) → 3Mg2+(aq)+2Al(s)
3Mg2+(aq)+2Al(s)
--> Ag+
e-
1. Ag
+
2. Au3+ + 3e- --> Au
3. F2 --> 2 F- + 2e4. Fe2+ + e- --> Fe3+
In this reaction, electrons are transferred from
1. Al to Mg2+
2. Al3+ to Mg
3. Mg to Al3+
4. Mg2+ to Al
Oxidation Reduction Reactions
Given the balanced equation
representing a redox reaction:
2Al + 3Cu2+ --> 2Al3+ + 3Cu
In any redox reaction, a
reactant can undergo a
decrease in oxidation
number by
Which statement is true about this
reaction?
1. Each Al loses 2e- and each Cu2+
gains 3e-.
2. Each Al3+ gains 2e- and each Cu
loses 3e-.
3. Each Al loses 3e- and each Cu2+
gains 2e-.
4. Each Al3+ gains 3e- and each Cu
loses 2e-.
1. losing electrons, only
2. losing protons, only
3. gaining electrons, only
4. gaining protons, only
Oxidation Reduction Reactions
Given the reaction shown:
Which species undergoes
oxidation?
1. Mg(s)
2. Cl-(aq)
3. H+(aq)
4. H2(g)
Which changes occur when Pt2+ is
reduced?
1. The Pt2+ gains electrons and its
oxidation number increases.
2. The Pt2+ loses electrons and its
oxidation number increases.
3. The Pt2+ gains electrons and its
oxidation number decreases.
4. The Pt2+ loses electrons and its
oxidation number decreases