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Regent’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-Up. What is the electron configuration of a sulfur atom in the ground state? (1) 2 – 4 (3) 2 – 8 – 4

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Regent’s Warm-Up

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Regent’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-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


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)

Oxidation Reduction Reactions

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 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 Mg0lost 2e-s, Mg0 is OXIDIZED

    2Mg0 2Mg+2 + 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+2 + 2e-s  Cu0


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

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 Mg4. Mg2+ to Al

Oxidation Reduction Reactions

3Mg2+(aq)+2Al(s)


Given 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

Oxidation Reduction Reactions


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