Chemistry - Chapter 7 - Oxidation and Reduction

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HYDROGEN BONDING

It is a type of bond where a hydrogen atom binds two strongly electronegative atoms. Example: H2O

                  (http://www.physicsofmatter.com/NotTheBook/Talks/Ice/Image7.gif)

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METALLIC BONDING

 The metallic bond is the force of attraction between two metal atomd . Example: Gold, Aluminium

(http://chemwiki.ucdavis.edu/@api/deki/files/1781/=D3d%20C2H6-1.bmp?size=webview)

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VAN DE WAAL'S FORCES

It is the weakest attraction between molecules or atoms.

(http://cdn.zmescience.com/wp-content/uploads/2013/07/van-der-waals-force.png)

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LONDON DISPERSION FORCES

It is a weak attractive intermolecular or interatomic force.

(http://4.bp.blogspot.com/_hm25eS2tXB0/TSnr1MS5z5I/AAAAAAAAADE/2tYY0-fCQgU/s1600/london.gif)

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REDOX REACTION

This is a reaction where one reactant is Oxidised and the other is Reduced

(http://www.chemguide.co.uk/inorganic/redox/redoxeqtn1.gif)

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OXIDATION

Oxidation = the loss of an electron 

Example : 

Cu -----> Cu2 + 2e- 

(http://figures.boundless.com/30775/full/redox-halves.png)

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REDUCTION

Reduction = the gaining of an electron

Example: 

S + 2e- -----> S2

(http://figures.boundless.com/30775/full/redox-halves.png)

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Finding Oxidation Number of an element

Look for any H's, O's, or F's in the equation 

1) Any element just by itself not in a compound, their oxidation number is 0 

ex: H2's oxidation number is 0 

2) The oxidation number of H is always +1, unless its just by itself (see #1) 

3) The oxidation number of O is always -2, unless its just by itself (see #1) 

4) The oxidation number of F is always -1, unless its just by itself (see#1) 

5) The sum of oxidation numbers in a compound add up to 0 (when multiplied by the subscripts!!!) (see above example) 

6) The sum of oxidation numbers for a compound is the charge (for example, PO4 has a charge of (-3) SOO...  

...oxidation no. of O = -2. (there are 4 O's = -8 charge on that side ) P must have an oxidation number of 5. (-8+5= -3), and -3 is the total charge of the compound. 

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Balanced REDOX Equation for Acid Solution

1. Add H2O

2. Add H+ ions

3. Add electrons (e-)

Example: 

I- + 3H20   ------> IO3- + 6H + 6e-

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Balanced REDOX Equation for Basic Solution

1. Add OH-

2. Add H+ ions

3. Add electrons (e-)

Example: 

S2- + 4OH- ---> SO4 2- + 4H+  + 8e

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REDOX LADDER

Chlorine 

(H = +1, Cl = +7, O = -2

HClO4   = +7  

ClO-  3  = +5

ClO-     = +1

Cl2       = 0

Cl-       = -1

HCl       = -1

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OXIDATION LADDER

Sulfur

SO4 -2   = +6

SO3         = +6

SO3 -2  = +4

SO2      = +4

S         = 0

H2S      = -2

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Activity Series - REDOX Equation for Reactions

Mg 2+ (aq) + 2e- ---> Mg(s)    = -2.37V ....1

Ag+ + e- ----> Ag(s)            = +0.80V  .....2

1. The most reactive has to be flipped

Mg (s) ----> Mg 2+ (ag) + 2e-      = +2.37V .....1a2. Make the no. of electrons the same as the first one

2Ag+ + 2e- ----> 2Ag(s)            = 0+.80V .... 2a

3. Write the equation (add both reactions together)

2Ag+ + 2e- + Mg(s) ---> 2Ag(s) + Mg2+(ag) +2e-   (1a+2a)

                        = +2.37V +0.80V = +3.17V (fast reaction)

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