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Electrolysis in Molten state

1. Molten Lead Bromide contains Lead ionand Bromide ions.

2. Lead ions attracted at cathode. Bromideions attracted at anode.

3. Lead receives two electrons to form Leadmetal. Pb

2++ 2e = Pb. Hence, Grey

precipitate is deposited.

4. Bromide ions attracted at cathode.Bromide donates two electrons to form

Bromine gas. 2Br- = Br2 + 2e. Hence,

Bromine gas is produced at cathode.

\\\

Electrolysis in Aqueous state

1. Copper(II) Sulphate contains Copper(II)ions, Sulphate ions, Hydroxide ions

and Hydrogen ions.

2. Copper(II) ions and Hydrogen ions willbe attracted at cathode. Copper(II)

ions will be selectively discharged

because the position of copper in the

Electrochemical series is lower than

Hydrogen.

3. Sulphate ions and Hydroxide ions willbe attracted to the anode. The

Hydroxide ions will be selectively

discharged because the position of

hydroxide ions in the electrochemicalseries is lower than Sulphate ions.

4. Cu2+ + 2e = Cu5. 4OH- = 2H2O + O2 + 4e6. Full equation : Cu2+ + 4OH- = 2CU +

2H2O + O2

7. The product at cathode is depositionof copper metal while at anode is

effervescence of oxygen gas.

8. For confirmatory test, effervescenceof oxygen gas is tested with glowing

wooden splinter; a rekindle of wooden

splinter is obtained for several

seconds.

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Arrangement of Cations in Electrochemical Series

K +

Na +

Ca 2+

Mg 2+

Al +Zn 2+

Fe 2+

Sn 2+

Pb 2+

H +

Cu 2+

Hg 2+Ag 2+

Au +

Increasing ability to discharge

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Extraction of Aluminium from

Aluminium Oxide

1. Alimunium oxide (Al2O3) is dissolvedinto melted cryolite (Na3AlF6)

2. The process lower the melting point of C.

3. The electrode are made of graphite.4. In molten state, Aluminium oxide will

dissociate into Al3+

ions and O2-

ions.

5. Al2O3 = 2Al3+ + 3O2-6. At cathode, 4Al3+ + 12e = 4Al7. At anode, 6O2- = 302 + 12e8. The aluminium metal is siphoned to

the ground and Oxygen gas will be

formed.

Purification of Metal

1. The pure copper is placed at cathodeand impure copper is placed at anode.

2. The electrolyte is made of copper-dissolving solution such as Copper(II)

sulphate.

3. At anode, Copper will dissolve to formCopper ions. Cu = Cu

2+

+ 2e4. At cathode, Copper ions will ionize

and accept two electron to form

Copper. Cu2+

+ 2e = Cu

5. The pure Copper will become thickerand the impure Copper will become

thinner.

Electroplating (coating) of Nickel

with Silver

1. Silver is placed at anode while a nickelmaterial ( jug, etc.) is placed at

cathode.

2. The solution is made form silver-dissolving solution such as Silver

nitrate.

3. At anode, the Silver dissolves to formSilver ions. Ag = Ag

++ e

4. At cathode, the Silver ions ionizes andaccept electron to form Silver metal.

Ag+

+ e = Ag

5. The formation of Silver metal willelectroplate (coat) the Nickel material.

6. The thicken of Silver will be stoppeduntil its thick enough.

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Ckg Fys M-Enhancing Technique

Insoluble Soluble

Ca2+

SO42-

Ammonium

Ba2+

Na+

Pb2+

I-

K+

Ag+

Br-

NO3-

Co3-

Cl-

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Alkane

Alkene

Alcohol

Carboxylic

Acid

Ester

Cracking

Dehydration

Al2O3 , H2SO4,

H3PO4

Oxidation

Potassium

Dichromate,

Potassium

Manganate(VI

Hydrogenation

+ H2

Hydration

+ H2O

Esterification

Concentrated

H2SO4

Substitution

+ Cl2

Chloroalkane

CnH2n+1

CnH2n

CnH2n+1OH

CnH2n+1COOH

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