Introduction to Oxidation and Reduction

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IB Chemistry Text

Green and Damji

TEXT 9.1 & 9.2

Types of Chemical Reactions ?

type of

reaction ?

1. Mg(s) + 2 HCl (aq) MgCl2 (aq) + H2 (g)

2. Pb(NO3)2 (aq) + 2 NaI (aq) PbI2 (s) + 2 NaNO3 (aq)

3. 2 H2O2 (aq) O2 (g) + 2 H2O (g)

4. 2 O2 (g) + CH4 (g) CO2 (g) + 2 H2O (g)

5. 2 H2 O (g) O2 (g) + H2(g)

another way to classify Types of Chemical Reactions

A. Acid Base Reactions

B. Precipitation Reactions

C. Redox Reactions

CaO (s) + 2 HCl (aq) CaCl2 (aq) + H2O (l)

H3PO4 (aq) + 3 NaOH (aq) Na3PO4 (aq) + 3 H2O (l)

Pb(NO3)2 (aq) + 2NaI (aq) PbI2 (s) + 2NaNO3 (aq)

which can be shortened to…Pb2+ + 2I- PbI2 (s)

2 Zn (s) + I2 (s) ZnI2 (aq)

2 Zn (s) + I2 (s) Zn2+ (aq) + 2 I- (aq)

Ca2+ + CO32- CaCO3

NH3 + H+ NH4+

Zn + 2HCl ZnCl2 + H2

Ca + F2 CaF2

________________

________________

________________

________________

Classify the following reactions as AB/PPT/RedOx

4.4

Oxidation-Reduction Reactions(electron transfer reactions)

2Mg + O2 2MgO

4.4

What is happening in this reaction? oxidation – loss of electrons: reduction – gain of electrons:

Helpful MneumonicsLEO the lion goes GER

Loss of Electrons is Oxidation

Gain of Electrons is Reduction

OIL RIG

Oxidation is the Loss of electrons

Reduction is the Gain of electrons

Oxidation numberThe charge the atom would have in a molecule (or anionic compound) if electrons were completely transferred to the more electronegative element.

1. Free elements (uncombined state) have an oxidation number of zero.

Na, Be, K, Pb, H2, O2, P4 =

2. In monatomic ions, the oxidation number is equal to the charge on the ion.

Li+, Li = ; Fe3+, Fe = ; O2-, O =

3. The oxidation number of oxygen is usually . In H2O2

and O22- it is .

4.4

4. The oxidation number of hydrogen is____except when it is bonded to metals in binary compounds. In these cases, its oxidation number is____.

6. The sum of the oxidation numbers of all the atoms in a molecule or ion is equal to the charge on the molecule or ion.

5. Group 1 metals are____, Group 2 metals are____and fluorine is always____.

HCO3-

O = ____ H = ____

3x(-2) + 1 + ? = -1

C = ____

Oxidation numbers of all the elements in HCO3

- ?

4.4

7. Oxidation numbers do not have to be integers. Oxidation number of oxygen in the superoxide ion, O2

-, is ____.

The oxidation numbers of elements in their compounds

4.4

The periodic table in your planner

includes the most common oxidation

numbers!

Na I O3

Na = ____ O = ____

3x(____) + ____ + ? = 0

I = ____

I F7

F = ____

7x(____) + ? = 0

I = ____

K2 Cr2 O7

O = ____ K = ____

7x(__) + 2x(__) + 2x(?) = 0

Cr = ____

What are the oxidation numbers of all the elements in the following compounds ?

4.4

More to know…An increase in oxidation number is oxidation.

A decrease in oxidation number is reduction.

The substance that is oxidized (loses e-; ox # increases)

is called the reducing agent.

The substance that is reduced (gains e-; ox # decreases)

is called the reducing agent.

4.4

Zn (s) + CuSO4 (aq) ZnSO4 (aq) + Cu (s)

ox:

red:

---------------------------------------

ttl:

____ is oxidized - is reducing agent

____ is reduced - is oxidizing agent

4.4

Copper wire reacts with silver nitrate to form silver metal.What is the oxidizing agent in the reaction?

ox:

red:

---------------------------------------

ttl:

____ is oxidized - is reducing agent

____ is reduced - is oxidizing agent

Types of Oxidation-Reduction Reactions

Combination Reaction (aka Synthesis)

A + B C

2Al + 3Br2 2AlBr3

Decomposition Reaction

2KClO3 2KCl + 3O2

C A + B

0 0 +3 -1

+1 +5 -2 +1 -1 0

4.4

Types of Oxidation-Reduction Reactions

Combustion Reaction

A + O2 B

S + O2 SO2

0 0 +4 -2

4.4

2Mg + O2 2MgO0 0 +2 -2

Single Displacement Reaction

A + BC AC + B

Sr + 2H2O Sr(OH)2 + H2

TiCl4 + 2Mg Ti + 2MgCl2

Cl2 + 2KBr 2KCl + Br2

Hydrogen Displacement

Metal Displacement

Halogen Displacement

Types of Oxidation-Reduction Reactions

4.4

0 +1 +2 0

0+4 0 +2

0 -1 -1 0

Disproportionation Reaction

Cl2 + 2 OH- ClO- + Cl- + H2O

Element is simultaneously oxidized and reduced.

Types of Oxidation-Reduction Reactions

Chlorine Chemistry

0 +1 -1

4.4

Chemistry in Action: Metals from the SeaRedox or not?

CaCO3 (s) CaO (s) + CO2 (g)

Mg(OH)2 (s) + 2HCl (aq) MgCl2 (aq) + 2H2O (l)

CaO (s) + H2O (l) Ca2+ (aq) + 2OH (aq)-

Mg2+ (aq) + 2OH (aq) Mg(OH)2 (s)-

MgCl2 (aq) Mg (s) + Cl2 (g)

_______________

_______________

_______________

____________

_______________

Write half reactions for one of the redox reactions above:

ox:

red: