Summary Chapter 12 - Sulfur CIE IGCSE Chemistry

TOPIC 12 – Sulfur

· SOURCES OF SULFUR:

 Sulfide ores.
 A by-product from the removal of sulfur from petroleum and natural gas.
 Found in its elemental state underground in the USA, Mexico and Poland.


· USES OF SULFUR DIOXIDE:

 As a bleach in the manufacture of wood pulp for paper.
 As a preservative for foods and drinks by killing bacteria.


· USES AND PURPOSES OF DILUTE SULFURIC ACID:

 Used as a catalyst in many organic reactions.
 Also used to clean the surface of metals.


· USES AND PURPOSES OF CONCENTRATED SULFURIC ACID:

 Used in car batteries, making phosphate fertilisers, soaps and detergents.
 It is also used to make acid drain cleaners and in the production of paints and dyes.
 Powerful oxidising agent.
 Powerful dehydrating agent.




· THE CONTACT PROCESS:

 STAGE 1 – oxidation of sulfur. ( S + O2 -> SO2 )
 STAGE 2 – oxidation of sulfur dioxide to sulfur trioxide using a catalyst (V 2O5). ( 2SO2 + O2 ⇌ 2SO3 )
 Stage 2 Conditions – Temperature = 450°C , Pressure = 2 atm.
 STAGE 3 (I) – SO3 is absorbed into a 98% sulfuric acid solution to form oleum. ( SO 3 + H2SO4 -> H2S2O7 )
 STAGE 3 (II) – Oleum is added to water to form concentrated sulfuric acid. ( H 2S2O7 + H2O -> 2H2SO4 )