Chemistry Metals and Electrolysis

Electrolysis is the breaking down of an ionic substance using electricity. The substance that is broken down is called the electrolyte. 

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  • Created by: Livy
  • Created on: 21-01-14 16:46

What Happens at Each Electrode?

Cations move to the Cathode, which is the NEGATIVE electrode. The equations for the Cathode look like this: Pb(2+) + 2e- = PB (reduction)

Anions move to the Anode, which is the POSITIVE electrode. The equations for the Anode look like this: 2bBr- = Br2 + 2e- (oxidation)

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The Reactivity Series

Reactivity Series:        Anions:

Potassium

Sodium

Lithium

Calcium

Magnesium

Aluminium

Carbon

Zinc

Iron

Tin

Lead

Hydrogen

Copper

Mercury

Silver

Gold

Platinum

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What Does This Mean?

If the metal is below Hydrogen in the Reactivity Series, you will produce the metal.

If the mtal is above Hydrogen in the Reactivity Series, you will produce Hydrogen.

If you have concentrated soloutions of halides (Chlorides, Bromides or Iodides) you will get the halogen (Chlorine, Bromine, Iodine)

With other negative ions, you will get Oxygen. If the Anion is below OH- you also produce Oxygen.

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Electrolysis of H2SO4

Product at Anode (Positive Electrode):

Oxygen

Half Equation:

OH- = 2H2O + O2 + 4e-

Product at Cathode (Negative Electrode):

Hydrogen

Half Equation:

2H+ = 2e- = H2

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The Diaphragm Cell

This is used to electrolyise Brine (Sodium Chloride Soloution). Brine is Saturated Salt (WaCl) Soloution.

Half Equation at Anode:

Cl- = Cl2 = 2e-

Half Equation at Cathode:

2H+ = 2e- = H2

The cell is designed to keep the positive and negative ions apart. If Cl2 and NaOH come in to contact, they produce Bleech instead of Sodium Hydroxide. A Membrane is used in the middle so only positibe ions can pass through. 

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Tests and Uses of Cl2, H2 and O2

O2: Relight a glowing splint

H2: Burns with a squeeky popo

Cl2: Bleaches Litmus Paper White

Uses of Chlorine: Bleech, Disinfectant and makes Plastic such as PVC

Uses of Hydrogen: Margerine, Hydrochloric Acid and Ammonia

Uses of Sodium Hydroxide: Soap, textiles, Ceramics and Purifying Wool

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Why do Electrolytes Conduct Electricity?

Electrolytes are molten compounds or compounds dissolved in a soloution. When Ionic Compounds are molten or dissolved in a soloution, they conduct electricity as there are now electrons free to move.

Not all ionic compounds can be dissolved molten, and some break into simpler substances before they reach melting point. 

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Aq Substances

When substances are Aq, they always produce Hydrogen at the Negative Electrode. 

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