Regent

1
Regents Warm-Up

• What is the electron configuration of a sulfur
  atom in the ground state?
• (1) 24 (3) 284
• (2) 26 (4) 286

2
Regents Warm-Up

• What is the electron configuration of a sulfur
  atom in the ground state?
• (1) 24 (3) 284
• (2) 26 (4) 286

3
Oxidation Reduction Reactions

• s

• AIM
• What are Oxidation-Reduction Reactions?
• Do Now
• If the conc. Of a product is increased how will
  the equilibrium state be affected?

4
Oxidation Reduction Reactions
What are they used for? Why are they important?

• Purifying metals (e.g. Al, Na, Li)
• Producing gases (e.g. Cl2, O2, H2)
• Electroplating metals
• Electrical production (batteries, fuel cells)

• Protecting metals from corrosion
• Balancing complex chemical equations
• Sensors and machines (e.g. pH meter)

5
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

6
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

7
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 ? 2Mg2O-2
• The oxidation of Mg goes from 0 to 2
• Since Mg0 lost 2e-s, Mg0 is OXIDIZED
• 2Mg0 ? 2Mg2 4e-

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Oxidation Reduction Reactions

• Current Definitions
• Reduction the Gain of Electrons
• Example Cu2O-2 H20 ? Cu0 H21O-2
• If you look closely oxygen is not reacting, its
  oxidation stays the same (-2)
• Copper goes from Cu2 to Cu0
• Copper gains 2e-s is REDUCED
• Cu2 2e-s ? Cu0

9
Oxidation Reduction Reactions

• Which particles are gained and lost during a
  redox reaction?
• (1) electrons
• (2) protons
• (3) neutrons
• (4) positrons

• What is the MAIN
• difference between the
• classical and current
• definitions?
• Oxygen is NOT
• required in the current
• definition

10
Oxidation Reduction Reactions

• Oxidation and Reduction reactions are opposite
  processes that occur simultaneously
• For something to lose an electron there must be
  something else that wants to gain that electron

• 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?
• 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.

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12
Oxidation Reduction Reactions

• Loss of Electrons is Oxidation
• Gain of Electrons is Reduction

• LEO the lion says GER

13
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

14
Oxidation Reduction Reactions

• Which half-reaction
• correctly represents
• reduction?
• 1. Ag --gt Ag e-
• 2. Au3 3e- --gt Au
• 3. F2 --gt 2 F- 2e-
• 4. Fe2 e- --gt Fe3

• Given the balanced ionic equation representing a
  reaction
• 2Al3(aq) 3Mg(s) ? 3Mg2(aq)2Al(s)
• In this reaction, electrons are transferred from
• 1. Al to Mg2 3. Mg to Al3
• 2. Al3 to Mg 4. Mg2 to Al

3Mg2(aq)2Al(s)
15
Oxidation Reduction Reactions

• Given the balanced equation representing a redox
  reaction2Al 3Cu2 --gt 2Al3 3Cu
• 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-.

• In any redox reaction, a reactant can undergo a
  decrease in oxidation number by
• 1. losing electrons, only
• 2. losing protons, only
• 3. gaining electrons, only
• 4. gaining protons, only

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Oxidation Reduction Reactions

• Given the reaction shownWhich 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