Regent’s Warm-UpRegent’s Warm-Up

What is the electron configuration of a sulfur

atom in the ground state?

(1) 2–4 (3) 2–8–4(2) 2–6 (4) 2–8–6

Regent’s Warm-UpRegent’s Warm-Up

What is the electron configuration of a sulfur

atom in the ground state?

(1) 2–4 (3) 2–8–4(2) 2–6 (4) 2–8–6

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?

Oxidation Reduction Reactions

• 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)

What are they used for? Why are they important?…

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 ReactionsCurrent Definitions

Take into account the charge of the ions and atoms involved in the reaction

• Oxidation – the Loss of ElectronsExample: 2Mg0 + O2

0 2Mg+2O-2

• The oxidation # of Mg goes from 0 to +2 • Since Mg0 lost 2e-s, Mg0 is OXIDIZED

2Mg0 2Mg+2 + 4e-

Oxidation Reduction ReactionsCurrent 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+2 + 2e-s Cu0

Oxidation Reduction Reactions

What is the MAINdifference between theclassical and currentdefinitions?

*Oxygen is NOTrequired in the currentdefinition*

• 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

• 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.

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

correctly represents

reduction?

1. Ag --> Ag+ + e-

2. Au3+ + 3e- --> Au

3. F2 --> 2 F- + 2e-

4. Fe2+ + e- --> 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)

Oxidation Reduction ReactionsGiven the balanced equation representing a

redox reaction:

2Al + 3Cu2+ --> 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

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