CHEMISTRYMake It Easy To Learns (MIATL PROJECT 1)

What is the relationship between CHAPTER 6(Form4) : Electrochemistry and CHAPTER 3 (Form 5): Oxidation and Reduction?

Let make it simpleThe formula related to this process is REDCAT and OXINODE.

What it mean exactly?

REDCAT - Reduction process occur at cathodeOXINODE - Oxidation process occur at anode

What is Oxidation process and Reduction process related both chapter ?

Oxidation Process - Loss of electron- Increase of oxidation number

Reduction Process - Gain of electron- Decrease of oxidation number

Loss or Gain electron how we know?

We have to method to know this:1. From the equation given or equation we make2. From the word discharge/release of electron

This also helps us to check whether the equation we make Correct or Not.

Example: voltaic cell - electrode used Mg and Ca

Cathode (Reduction): Mg2+ + e MgAnode (Oxidation): Ca Ca2+ + e

Did you see now?

Increase/decrease of oxidation number? I don’t understand this?

Let look at the example given:

Look at the charge

Cathode (Reduction): Mg2+ + e Mg 2+ 0Anode (Oxidation): Ca Ca2+ + e 0 2+

This also mean at the Cathode liquid change to solid and at the anode is Vice Versa

What is the deferent between Electrolytic and Voltaic cell?

Electrolytic Cell Voltaic CellElectrical Reaction to Chemical Reaction Chemical Reaction to Electrical Reaction

Cation and Anion Cation onlyThe ion discharge at cathode(Cation) and The ion discharge at cathode and anode is

Anode(Anion) Cation onlyCathode(Negative terminal) and

Anode(Positive terminal)Cathode(Positive terminal) and

Anode(Negative terminal)Required a source of electric current Does not required a source of electric current

Electrode from same material Two different metals We have 2 state of electrolytic cell right? What it is?

Molten compound and aqueous solution

What is the different?

MOLTEN COMPOUND AQEUOUS SOLUTIONDO NOT HAVE ANY FACTOR AFFECT DISCHARGE OF ION

HAVE 3 THREE FACTOR DISCHARGE OF ION

DO NOT HAVE OH- AND H+ HAVE OH- AND H+

In molten compound the ion discharge is own compound

Example:Molten PbBr the ion discharge is Pb2+ and Br-

In aqueous solution we have three factors affect the discharge of ion

1. Position of ion in Electrochemical Series2. Concentration of ion in the electrolyte3. Types of electrode used

Can you explain me the factor above? Sure.

1. Position in Electrochemical series (ECS)

Example:Cathode: Zn2+ and H+ the ion discharge is Zn2+.This because H+ has located lower than Zn2+ in ECS.

Zn2+ + 2e ZnAnode: Br- and OH- the ion discharge is OH-. This because OH- has located lower than Br- in ECS.

4OH- H2O + 2O2 + 4e(memorise this)

2. Concentration ion in electrolyte the ion discharge same with molten compound because the concentration of water(OH- and H+) is very low and do not choose to discharge

3. Type of Electrode

The electrode used must another from carbon and platinum because they are inert electrode

Example:The electrode used is Cu.

Cathode: Cu2+ + 2e CuAnode: Cu Cu2+ + 2e

This process used in:

1. Extraction of metals2. Purification of metals3. Electroplating of metals

Caution the solution used must be the same with electrode used.

Example:Cu electrode used. The solution use CuSO4.

Now I know about Electrolytic Cell but what about Voltaic Cell?

Okay let me explain

In Voltaic Cell we have only one factor affect the discharge of ion.The factor is Position in ECS.The ion occur in this Voltaic Cell is only a Cation.The cation selective to discharge(release electron) is the ion has located higher in ECS

Example:Zn2+ and Mg2+ the ion selective to discharge is Mg2+.

Anode: Mg Mg2+ + 2eCathode: Zn2+ + 2e Zn Is that the Voltaic Cell Process same with Rusting Process?

Almost

Almost, what is the different actually?

Voltaic Cell Process Rusting ProcessThe discharge of ion at cathode is Cation The discharge of ion at cathode is water

2O2 + H2O + 4e 4OH-

At anode both are same factor affect the discharge of ion

Can you explain about rusting process?

Sure. To form a rusting,Fe(OH)2 at anode the ion have to discharge must be Fe2+. Thus we can prevent rusting by three methods:

1. Alloying2. Sacrificial Protection

Iron connected with more electropositive metal/higher place than metal in ECS.3. Protective Coating/Painting

What about voltaic cell process and Redox reaction, is that same?

No, now I explain to you.

Voltaic Cell Redox reactionCathode(positive terminal) and Anode(negative terminal)

At Cathode and Anode, ion selective to discharge depend in position in ECS

At Cathode and Anode, ion discharge depend on the solution given

Example of Redox Reaction:

What do I need to memorise in this 2 chapter?

1. ECS

2. Some equation in redox reaction

3. The colour of solution or metal

4. The indicator used to detect the present of some solution

That only thing you have to know in this two chapter...

So Make It Easy Learn...

Thank you...

Author:Muhd Ashraf bin ShaharudinForm5 (2010)