C11.2, C12, C13

Question 1

How is sulfur mainly used?

Answer 1

The manufacture of sulphuric acid

Question 2

Explain how sulfuric acid is made by the contact process

Answer 2

Stage 1:
oxidation of sulfur
S + O2 -> SO2

Stage 2:
Oxidation of SO2 to SO3 using catalyst V2O5 (vanadium oxide)
2 SO2 + O2 <=> 2 SO3
Conditions:
Temp -> 450°C
Reaction is exothermic, meaning the formation of SO2 is favored
Optimum temp is a compromise between -> high rate of reaction (catalyst helps) and the yield of SO3
Pressure:
Increased pressure -> SO3 favored
Reaction done slightly above atmospheric level -> too expensive and not worth more

Stage 3:
SO3 is absorbed into solution of sulphuric acid (produces oleum)
SO3 + H2SO4 -> H2S2O7
Not directly added to water because it would produce mist of sulfuric acid -> difficult to condense and dangerous

H2O + H2S207 -> 2 H2SO4
Oleum added to water -> concentrated sulfuric acid

Question 3

What are the properties of sulfuric acid?

Answer 3

Corrosive
Oxidizing agent
Dehydrating agent

Question 4

What are the uses of sulfuric acid?

Answer 4

Clean metals
Fertilizer
Soaps and detergents
Car batteries
Acid drain cleaners

Question 5

How is lime manufactured?

Answer 5

Lime (CaO) is manufactured from limestone (calcium carbonate (CaCO3))

Limestone -thermal decomposition-> lime + CO2

Question 6

How is slaked lime and lime water produced?

Answer 6

Slaked lime (calcium hydroxide (Ca(OH)2))
Water + lime (CaO) -> slaked lime
Mixed slowly because it is exothermic

Limewater
Slaked lime in water -> slightly alkaline
CO2 added to limewater -> white precipitate -> calcium carbonate (cycle repeated)

Question 7

What are the uses of lime and lime products?

Answer 7

Used to treat acidic soil and industrial waste (SO2 + CaO -> doesn’t go into the air and no acid rain)