oxidation and reduction in terms of oxygen chemistry

7/24/2019 Oxidation and Reduction in Terms of Oxygen Chemistry

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Oxidation and Reduction in Terms of Oxygen/Hydrogen Transfer

Understanding Oxidation and Reduction

1. Oxidation and reduction can be understood from the aspect of:a. Losing or gaining oxygen

b. Losing or gaining hydrogen

c. Transferring of electron

d. Changing of oxidation number

Oxidation and Reduction in Terms of Oxygen Transfer

1. Oxidation is the process of gaining oxygen.

2. Reduction is the process of losing oxygen.

3. or example! in the extraction of iron from its ore:

"ron#"""$ oxide loses oxygen. "ron#"""$ oxide is reduced to iron. This is a reduction process.

Carbon monoxide gains oxygen. Carbon nonoxide is oxidised to become carbon dioxide. This is

an oxidising process.

Oxidation and Reduction in Terms of Hydrogen Transfer

1. Oxidation is the process of losing hydrogen.

2. Reduction is the process of gaining hydrogen.

3. or example! ethanol can be oxidised to ethanal:


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%mmonia loses hydrogen. %mmonia is oxidised to become nitrogen. This is an oxidation

process.

&romine gains hydrogen. &romine is reduced to become hydrogen bromide. This is a

reduction process.

Example:

Combustion of Magnesium in Air

'agnesium is oxidised to become magnesium oxide.

Displacement of copper!!" oxide by Carbon

Copper#""$ oxide is reduced to become copper metal

Carbon is oxidised to become carbon dioxide.


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Displacement of lead!!" oxide by #inc

(inc is oxidised to become )inc oxide.

Lead#""$ oxide is reduced to become lead metal

Reaction bet$een Magnesium and %team

*ater is reduced to become hydrogen gas.

'agnesium is oxidised to become magnesium oxide.

Hydrogen %ulp&ide Reacts $it& C&lorine

+ydrogen sulphide is oxidised to become sulphur.

Chlorine is reduced to become hydrogen peroxide.


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Copper!!" oxide Reacts $it& Ammonia

Copper#""$ oxide is reduced to become copper#""$ metal.

%mmonia is oxidised to become nitrogen gas.

Oxidation and Reduction in Terms of Electron Transfer

Oxidation occurs ,hen a reactant loses electron.

Reduction occurs ,hen a reactant gain of electron.

Example:

CuO - 'g Cu - 'gO

"n this reaction!a. copper #""$ ion in copper#""$ oxide gains 2 electrons to form copper metal.

+alf e/uation:

Cu2-- 2e Cu

This is a reductionprocess.

b. 'agnesium metal loses 2 electrons to form magnesium ions in magnesium

oxide.

+alf e/uation:

'g 'g2-- 2e

This is a oxidationprocess.


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%ummary

1. 'agnesium is oxidisedbecause it loses2 electrons to form magnesium ion! 'g2-.

2. Copper#""$ oxide is reduced because copper#""$ ion gains 2 electrons to form copper

metal! Cu.

Oxidation %tates Oxidation 'umbers"

Oxidation state sho,s the total number of electrons ,hich ha0e been remo0ed from an element#a positi0e oxidation state$ or added to an element #a negati0e oxidation state$ to get to its present

state.

Oxidation %tate of %ome Elements

1. The oxidation state of an element is )ero.

ExampleElement Oxidation %tate

'g

+2

&r2

2. or a simple ion ,ith single atom! the oxidation state is e/ual to the charge.

Example

!on Oxidation %tate

Cu2- -2

&r 1

O2 2

%l3- -3

3. ome elements almost al,ays ha0e the same oxidation states in their compounds:

Example ()The oxidation state of oxygen is al,ays 2 except peroxide! ,hich is 1.Compound Oxidation state of

oxygen

+2O 2

+2O4 2


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(nO 2

5ClO3 2

+2O2 1

Example *)The oxidation state of hydrogen is al,ays -1 except hydride! ,hich is 1.

Compound Oxidation state of

&ydrogen

6+3 -1

+Cl -1

6aO+ -1

'g+2 1

6a+ 1

4. The sum of the oxidation states of all the atoms or molecule in a neutral compound is )ero.

Example:

!on %um of Oxidation %tate

+2O

CO2

6+3

7. The sum of the oxidation states of all the atoms in an ion is e/ual to the charge on the ion.

Example:

!on %um of Oxidation %tate

6O3 1

CO32

2

8O43 3

6+4- -1


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+or,ing Out t&e Un,no$n Oxidation %tate of an Element in A Compound

The sum of the oxidation state of each element in a compound are e/ual to the charge of

the compound.

This rule can be used to find the un9no,n oxidation number of an element is a

compound.

Example (

ind the oxidation state of all the elements in a Chlorate#$! ClO3ion.

Ans$er:

Oxidation number of O ; 2

Oxidation number of Cl ; x

x - 3#2$ ; 1

x ; 1 - < ; -7

Example *

ind the oxidation state of all the elements in a 8otassium manganate#""$! 5'nO 4ion.

Ans$er:

Oxidation number of 5 ; -1=

Oxidation number of O ; 2

Oxidation number of 'n ; x

#-1$ - x - 4#2$ ;

x ; 1 - >x ; -?

Example -

ind the oxidation state of all the elements in an %mmonium ion! 6+4-ion.

Ans$er:


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Oxidation number of + ; -1

Oxidation number of 6 ; x

x - 4#-1$ ; -1

x ; -1 4

x ; 3

oxidation and reduction in terms of oxygen chemistry

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