The allotropes of sulphur Manufacture of sulphuric acid by the contact process Today’s lesson

• The allotropes of sulphur

• Manufacture of sulphuric acid by the contact process

Today’s lesson

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Question

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Allotropes of sulphur

Sulphur molecule consists of 8 atoms in a ring form.

Allotropes of sulphur

It melts at 115°C (low) which is because of its simple molecular structure.

Allotropes of sulphur

As it is heated more strongly, the rings break and join together to make long chains. It becomes sticky.

Allotropes of sulphur

Near to the boiling point, the chains start to break, the liquid is less viscous and it starts to evaporate.

Allotropes of sulphur

When it evaporates it forms S2 molecules.

Allotropes of sulphur

If it is poured quickly into water, plastic sulphur is made.It is “frozen” in long chain molecules like rubber.

Allotropes of sulphur

It will eventually change back into S8.

Allotropes of Sulphur

Sulphuric acid – The contact process

The contact process

• Sulphur is burnt in air

S(l) + O2(g) SO2(g)

The contact process

• A vanadium oxide catalyst helps the sulphur dioxide react with oxygen to form sulphur trioxide

2SO2(g) + O2(g) 2SO3(g)

reversible

The contact process

• sulphur trioxide reacts with water to form sulphuric acid (in a mixture of 98% sulphuric acid and 2% water)

SO3(g) + H2O(l) H2SO 4(l)

The contact process

Uses of sulphuric acid

• Making fertilisers (ammonium sulphate)

Uses of sulphuric acid

• Tanning leather

Uses of sulphuric acid

• Making soapless detergents

Uses of sulphuric acid

• Cleaning metals

Sulphur dioxide SO2

Produced by burning sulphur (or burning fossil fuels)

S(l) + O2(g) SO2(g)

In water

Dissolves to form sulphurous acid

SO2(g) + H2O(l) H2SO3(aq)

Oxides of nitrogen

Nitrogen is generally an unreactive gas, and needs fairly extreme conditions to get it to react with oxygen

Nitric oxide, NO

Lightning brings about the direct union of nitrogen and oxygen in the air to produce small amounts of nitric oxide, as does the high temperatures produced in car engines.

Nitric oxide, NO

It is a toxic air pollutant, often linked with asthma and allergic responses

Nitrous oxide, N2O

Formed when ammonium nitrate, NH4NO3, is heated. A colourless gas with a pleasing odour and sweet taste, is used as an anesthetic for minor operations, especially in dentistry.

Nitrous oxide, N2O

It is called laughing gas because of its intoxicating effect. It is alsowidely used as a propellant in aerosol cans of whipped cream!

Nitrogen dioxide, NO2

In the presence of excess oxygen, nitric oxide, NO, will be converted to nitrogen dioxide,NO2. Nitrogen Dioxide is a reddish brown, toxic gas at room temperature. NO2 condenses to a brown liquid, but freezes to a colourless solid.

Nitrogen dioxide, NO2

Nitrogen Dioxide has been used as a catalyst in certain oxidation reactions; as a nitrating agent for organic compounds; as an oxidizing agent; as a rocket fuel; and as a flour bleaching agent

Today’s lesson

• Electrolysis of brine

Brine?

Brine is salty water (sodium

chloride solution)

Electrolysis of brine

Electrolysis of brine

• Hydrogen is produced at the cathode

• Chlorine is produced at the anode

• The solution remaining is sodium hydroxide

Electrolysis of brine

• Hydrogen is produced at the cathode

• Chlorine is produced at the anode

• The solution remaining is sodium hydroxide

Cathy’s Ankles (CatHy’s AnCl)

Electrolysis of brine

• Hydrogen is produced at the cathode

• Chlorine is produced at the anode

• The solution remaining is sodium hydroxide

Cathy’s Ankles (CatHy’s AnCl)

Copy please!

Electrolysis of brine

• Cathode (-)

2H+(aq) + 2e- H2(g)

(SODIUM IS NOT FORMED (the sodium ion is more stable than the hydrogen ion in water H2O H+ + OH-))

• Anode (+)

2Cl-(aq) – 2e- Cl2(g)

Electrolysis of brine

• Cathode (-)

2H+(aq) + 2e- H2(g)

(SODIUM IS NOT FORMED (the sodium ion is more stable than the hydrogen ion in water H2O H+ + OH-))

• Anode (+)

2Cl-(aq) – 2e- Cl2(g)

Copy please!

Chemicals from salt

Chemicals from salt

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