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• The allotropes of sulphur
• Manufacture of sulphuric acid by the contact process
Today’s lesson
Stick it in!
Can you stick the sheet in and read the instructions?
Question
Can you answer the question please?
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)
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)
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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)
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Chemicals from salt
Chemicals from salt
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