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The Chemistry of Sodium Chloride. L.O. I know the products of electrolysing molten sodium chloride and sodium chloride solution. I know what these products are used to make. Recapping Alcohols – backs of books. Name these alcohols:- 1. C 2 H 5 OH 2. C 5 H 11 OH

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The chemistry of sodium chloride l.jpg

The Chemistry of Sodium Chloride

L.O.

I know the products of electrolysing molten sodium chloride and sodium chloride solution.

I know what these products are used to make.


Recapping alcohols backs of books l.jpg
Recapping Alcohols – backs of books

Name these alcohols:-

1. C2H5OH

2. C5H11OH

Write the molecular formula of these

alcohols:-

3. Propanol

4. Methanol

Name the two ways of producing ethanol



How does the chlorine form l.jpg
How does the chlorine form? molten Sodium Chloride

In the electrolysis of molten NaCl, the negative chloride ions

(Cl-) are attracted to the

positive electrode.

Here, the Cl- ionslose

electrons to make

chlorine atoms, which then

form chlorine molecules (Cl2).

oxidized

  • Are the Cl- ions oxidized or reduced?

  • How many electrons are lost by each Cl- ion?

  • How many Cl- ions join to make a Cl2 molecule?

  • What is the half-equation for this redox process?

one

two

2Cl-  Cl2 + 2e-(oxidation)


How does the sodium form l.jpg
How does the sodium form? molten Sodium Chloride

In the electrolysis of molten NaCl, the positive sodium ions

(Na+) are attracted to the

negative electrode.

Na+

Here, the Na+ ions

gain electrons to make

sodium atoms.

Na

Na+

reduced

  • Are the Na+ ions oxidized or reduced?

  • How many electrons are gained by each Na+ ion?

  • What is the half-equation for this redox process?

one

Na+ + e- Na(reduction)



Electrolysis of nacl solution l.jpg
Electrolysis of NaCl solution molten Sodium Chloride


Why is sodium not formed l.jpg

For all ionic compounds containing molten Sodium Chloridea metal that is more reactive than hydrogen, electrolysis of a solution of the compound will produce hydrogen rather than the metal.

Why is sodium not formed?

In the electrolysis of sodium chloride solution, the Na+ions might be expected

to form sodium at the negative electrode.

Instead, hydrogen gas is produced here.

This is because sodium chloride solution also contains H+ ions from some of the water: H2O (l)  H+ (aq) + OH- (aq).

At the negative electrode, the H+ ions compete with the Na+ions. The H+ ions gain electrons; the Na+ ions stay in solution.


How does the hydrogen form l.jpg
How does the hydrogen form? molten Sodium Chloride

In the electrolysis of NaCl solution, the positive hydrogen ions

(H+) are attracted to the

negative electrode.

Here, the H+ ions

gain electrons to make

hydrogen atoms, which then

form hydrogen molecules (H2).

reduced

  • Are the H+ ions oxidized or reduced?

  • How many electrons are gained by each H+ ion?

  • How many H+ ions join to make a H2molecule?

  • What is the half-equation for this redox process?

one

two

2H+ + 2e- H2(reduction)


How does the sodium hydroxide form l.jpg

2NaCl (aq) + 2H molten Sodium Chloride2O (l)  H2 (g) + Cl2 (g) + 2NaOH (aq)

How does the sodium hydroxide form?

Sodium chloride solution has four types of ions:

  • Na+ and Cl- ions from the sodium chloride

  • H+ and OH- ions from the water.

The Cl- ions form chlorineat the positive electrode and the H+ ions form hydrogenat the negative electrode. So, what’s left?

Na+ and OH- ions are left behind and so a solution of sodium hydroxide (NaOH)is formed.

What is the overall equation for the electrolysis of a sodium chloride solution?


Hydrogen or metal l.jpg

potassium molten Sodium Chloride

sodium

calcium

magnesium

aluminium

(carbon)

Product at the negative electrode

Ionic compound

zinc

iron

potassium chloride

lead

copper sulphate

(hydrogen)

copper

sodium bromide

silver

silver nitrate

gold

zinc chloride

platinum

Hydrogen or metal?

If an ionic compound containsa metal

that is more reactive than hydrogen, electrolysis of a solution of the compound will produce hydrogen, not the metal.

increasing reactivity

Complete the table for these compounds.

hydrogen

copper

hydrogen

silver

hydrogen


Products of electrolysis of nacl solution l.jpg
Products of electrolysis of NaCl solution molten Sodium Chloride

The electrolysis of sodium chloride solution produces three very useful products:

  • Chlorineused for killing bacteria in water, for bleach and making plastics like PVC.

  • Hydrogenused for making margarine and fertilizers, and for rocket fuel and fuel cells.

  • Sodium hydroxideused in many chemical reactions, such as making soap,neutralizing acids and making paper.

Chlorine is expected as a product of this process but hydrogen and sodium hydroxide are surprising products.


Homework answer questions on worksheet to review the lesson at home l.jpg

Homework molten Sodium Chloride

Answer questions on worksheet to review the lesson at home


Video on chloro alkali industry l.jpg
Video on Chloro-alkali Industry molten Sodium Chloride


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