Redox Reaction

Oxidation

-Gains Oxygen

-Loss hydrogen

-Loss electron

-Increase in oxidation number

Reduction

-Loss oxygen

-Gain hydrogen

-Gain electron

-Decrease in oxidation number

Oxidizing agent

Undergoes reduction

Reducing agent

Undergoes oxidation

Redox reaction

Oxidation process and reduction process occurs simultaneously

Reducing agent (Galvanic cell)

• Iron(II) sulphate solution

• Potassium bromide solution (KBr)

• Potassium iodide solution (KI)

Oxidizing agent (Galvanic cell)

• Acidified KMnO4 solution

• Bromine Water

• Chlorine water

• Acidified K2Cr2O7 solution

Positive terminal for galvanic cell (U-tube)

• Where reduction occurs

• Where oxidizing agent is at

Nagative terminal for galvanic cell (U-tube)

• Where oxidation occurs

• Where reducing agent is at

Function of sulphuric acid (U-tube) (Galvanic cell)

Allow ions to pass through it to complete the circuit

CuO

Copper (II) oxide

Cu_2O

Copper (I) oxide

MnO_2

Manganate (IV) oxide

Mn_2O_7

Manganate (VII) oxide

K_2Cr_2O_7

Potassium dichromate (VI)

KMnO_4

Potassium manganate (VII)

Fe^{2+} (Color)

Green

Fe^{3+} (Color)

Brown

Br^{-} (Color)

Colorless

Cr_2O_7^{2-} (Color)

Orange

Cr^{3+} (Color)

Green

MnO_{4-}^{-} (Color)

Purple

Mn^{2+} (Color)

Colorless

Cl_2 (Color)

Greenish yellow

Cl^{-} (Color)

Colorless

Cu^{2+} (Color)

Blue

Test for Fe^{2+}

Add sodium hydroxide solution, green precipitate is formed

Test for Fe^{3+}

Add sodium hydroxide solution, brown precipitate is formed

Test for Zn^{2+}

Add sodium hydroxide solution, white precipitate dissolves in excess sodium hydroxide solution

Test for Br_2

Add 1,1,1-trichloroethane, brown color is formed

Test for I_2

Add 1,1,1-trichloroethane, purple color is formed

Why does potassium chloride solution does not have changes occurs when add 1,1,1-trichloroethane?

No changes can be observed since chlorine is more reactive than bromine/iodine

In voltaic cell what is the change in energy

Chemical energy to electrical energy

How to determine negative terminal for Voltaic cell

• Refer to SEP series

• Metal with more negative E° value is the negative terminal

• electron move from negative terminal to positive

If the highest one is replaced with even higher one in SEP what will happen to voltmeter reading?

• voltmeter needle will deflect more

• Because E°value of the higher one is more negative then the previous highest one

How to write cell notation for voltaic cell

Example:

• Zn^{2+}\left(aq\right)

Porous pot/Salt bridge function

Allow ions to pass through it to complete the circuit

Electrolyte

Electrolyte are substances that can conduct electricity when they are in molten state or aqueous solution and undergo chemical changes

Electrolysis process

The process whereby compounds in their molten or aqueous state are broken down into their elements by passing electricity through it

In electrolysis what are anode and cathode

• Anode is the electrode that connects to the positive terminal of a battery

• Cathode is the electrode that connects to the negative terminal of a battery

En