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IC S4 P1+2 – First hand investigation and analyse information from secondary sources to predict and explain different products of aqueous and molten NaCl Use this in conjunction with the worksheet!. Electrolysis of salt 3. Na + ions move to the cathode but do not accept electrons.

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Electrolysis of salt 3

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Electrolysis of salt 3

IC S4 P1+2 – First hand investigation and analyse information from secondary sources to predict and explain different products of aqueous and molten NaClUse this in conjunction with the worksheet!


Electrolysis of salt 3

Electrolysis of salt 3

  • Na+ ions move to the cathode but do not accept electrons.

  • It is the hydrogen ions (from water) that gain electrons.

  • As a result hydrogen gas is formed at the cathode.


Electrolysis of salt 3

Na+

Cl-

H

H

H

O

O-

RED CAT Cathode

  • H2O is more easily reduced than Na+

  • H2O(l) + e-  ½ H2(g)+ OH-(aq)

  • This means that H2(g) and OH- is formed at the negative cathode.

  • Na+is left behind.

H+


Electrolysis of salt 1

Electrolysis of salt 1

At the ANODE.

  • Why do you think that even though the reduction potentials predict that oxygen will be formed, we get chlorine?

  • Standard Reduction Potentials (1M)

Chlorine gas is formed

2Cl- - + 2e-

Cl2


Electrolysis of salt 11

Electrolysis of salt 1

AN OX Anode

  • Chloride and water have similar reduction potentials.

  • But the NaCl is 2M concentration and in this condition it has a lower potential than water and is more easily oxidised.

  • 2Cl- Cl2 + 2e-

Chlorine gas is formed

2Cl- - + 2e-

Cl2


Electrolysis of salt 4

No change “Spectator ion”

Na+

Cl-

Changed into chlorine gas at anode

H

Changed into hydrogen gas at cathode

O-

No change “Spectator ion”

Electrolysis of salt 4

  • What happens to the various ions?

H+


Electrolysis of salt 5

Na+

Cl

Cl

Na+

Cl-

H

H

H

H

O-

O-

H+

Solution

Electrodes

Electrolysis of salt 5

  • Sodium hydroxide is what is left in the solution at the end of electrolysis


Electrolysis of salt 3

Electrolysis of salt


Complete q1 7 on the worksheet

Complete Q1-7 on the worksheet.


What happens if we dilute the concentration of nacl

What happens if we dilute the concentration of NaCl?


What happens if we dilute the concentration of nacl1

What happens if we dilute the concentration of NaCl?

RED CAT Cathode

  • H2O is more easily reduced than Na+

  • H2O + e- ½ H2+ OH-

  • This means that H2(g) and OH- is formed at the negative cathode.

  • Na+is left behind.


What happens if we dilute the concentration of nacl to 1 00 m

What happens if we dilute the concentration of NaCl to 1.00 M?

AN OXAnode

Under Standard conditions H2O is more easily oxidised than Cl-.

H2O + 2H+ + ½ O2+ 2e-

  • This means that H+ and O2 is formed at the negative cathode.


Complete q8 10

Complete Q8 - 10.


What do you predict would happen if we could perform electrolysis on molten nacl

What do you predict would happen if we could perform electrolysis on molten NaCl?


Electrolysis of salt 3

Molten NaCl.Contains only Na+ and Cl-ions.Anode (Oxidation)2Cl-(l)  Cl2(g)+2e-Cathode (Reduction)Na+(l)+ e-Na(l)


Electrolysis of salt 3

Uses of the products of electrolysis of NaCl(aq). (You do not need to know all of this but it is interesting)


Electrolysis of salt 3

Electrolysis of salt - summary


Uses of chlorine 1

Sterilisation of water

e.g. swimming pools

and drinking water

Bleaching agent,

e.g. paper industry

Uses of chlorine 1

electrolysis

Sodium

chloride

‘rock salt’

solution

Chlorine

gas


Uses of chlorine 2

Manufacture of HCl

continued

Uses of chlorine 2

Sterilisation of water

e.g. swimming pools

and drinking water

electrolysis

Sodium

chloride

‘rock salt’

solution

Bleaching agent,

e.g. paper industry

Chlorine

gas

Manufacture of

Cl-containing

organic chemicals


Uses of chlorine 3

Uses of chlorine 3

Manufacture of PVC and

other plastics

Manufacture of HCl


Uses of chlorine 4

Uses of chlorine 4

Manufacture of PVC and

other plastics

Manufacture of HCl

Pesticides

Manufacture of

Cl-containing

organic chemicals

Solvents, e.g. solvent for

tippex, & ‘dry cleaning’

dyes


Uses of sodium hydroxide 1

Uses of sodium hydroxide 1

Extraction of aluminium

Manufacture of soap

Sodium

chloride

‘rock salt’

solution

electrolysis

Sodium

hydroxide

Manufacture of Paper


Uses of sodium hydroxide 2

Uses of sodium hydroxide 2

Extraction of

aluminium

Manufacture of soap

Sodium

chloride

‘rock salt’

solution

Sodium

hydroxide

solution

electrolysis

Manufacture of Paper

Textiles (wool,

cotton)


Uses of sodium hydroxide 3

Uses of sodium hydroxide 3

Extraction of

aluminium

Manufacture of soap

Sodium

chloride

‘rock salt’

solution

Sodium

hydroxide

solution

electrolysis

Manufacture of Paper

Textiles (wool,

cotton)

Neutralisation

of acid effluents


Electrolysis of salt 3

Uses of Cl and NaOH


Uses of products from salt

bleach

Sodium hydroxide

soap

Aluminium extraction

Acid neutralisation

salt

chlorine

Hydrochloric acid

hydrogen

Organic chlorides

pvc

dyes

Uses of products from salt

Join the appropriate substances with arrows.


Electrolysis of salt 3

Purify

Salt Water

Why Purify?

Mg2++

Ca2++

SO42-+

Fe2++


Electrolysis of salt 3

Purify

Salt Water

Why Purify?

Mg2++2OH-Mg(OH)2

Ca2++CO32-CaCO3

SO42-+Ca2+CaSO4

Fe2++2OH-Fe(OH)2


Electrolysis of salt 3

Net ionic equation?

Ignore the spectator ion(s)

2H2O+2Cl-Cl2+H2+ 2OH-

Full equation?

Include the spectator ion(s)


Electrolysis of salt 3

Net ionic equation?

Ignore the spectator ion(s)

2H2O+2Cl-Cl2+H2+ 2OH-

Full equation?

Include the spectator ion(s)

2H2O+2NaClCl2+H2+ 2NaOH


Electrolysis of salt 3

Mercury ProcessDiaphragm ProcessMembrane Process

Mercury process actually produes Na at the cahode…

Na then reacts with water

2Na + H2O 2NaOH+ H2


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