1. Learning Objectives https://www.youtube.com/watch?v=xjLUJ-7m5v8
understand the role of sulphuric acid as an acid and as an oxidising agent
recall at least one process for the manufacture of sulphuric acid in terms of an equilibrium process and its major uses as an industrial chemical
understand the environmental impact of sulphuric acid manufacture
evaluate ways of minimising these environmental impacts
Contact Process Fuse School (5 min)

2. World Production of Sulfuric Acid

3. Sulphur is a waste product and VERY cheap

4. The contact process H2SO4 manufacture
Or PbS or FeS2 or other sulfur ores
4 FeS2(l) + 11O2(g)  Fe2O3(s) SO2(g)
2 PbS(l) + 3O2(g)  2 PbO(s) SO2(g)
Sulphur is so cheap why bother with this process!!!
Iron(II)sulfide (pyrite), fools gold S8
Sulphur is burnt in air
S(l) + O2(g)  SO2(g)

5. EQUILIBRIUM: 2nd Reaction Reaction Summary
Rx 1: S(l) + O2(g)  SO2(g)
V2O5
Rx 2: 2SO2(g) + O2(g) SO3(g) ∆H = -196 KJ/mol
This reaction is the only one of the 3 processes we can change because it us in equilibrium, as we did with the Haber process.

6. FACTORS AFFECTING THE POSITION OF EQUILIBRIUM CONCENTRATION SUMMARY
Le Chatelier
2SO2(g) + O2(g) SO3(g) + Energy
INCREASE CONCENTRATION OF A REACTANT
EQUILIBRIUM MOVES TO THE RIGHT
THE EFFECT OF CHANGING THE CONCENTRATION ON THE POSITION OF EQUILIBRIUM
DECREASE CONCENTRATION OF A REACTANT
EQUILIBRIUM MOVES TO THE LEFT
INCREASE CONCENTRATION OF A PRODUCT
DECREASE CONCENTRATION OF A PRODUCT
Predict the effect of increasing the concentration of O2 on the equilibrium position
2SO2(g) + O2(g) SO3(g)
EQUILIBRIUM MOVES TO RHS
Predict the effect of decreasing the
concentration of SO3 on the equilibrium position
EQUILIBRIUM MOVES TO RHS

7. AFFECTING THE POSITION OF EQUILIBRIUM
Le Chatelier
PRESSURE
When studying pressure changes, we consider the number of gaseous molecules only.
INCREASE PRESSURE
MOVES TO THE SIDE WITH FEWER GASEOUS MOLECULES
DECREASE PRESSURE
MOVES TO THE SIDE WITH MORE GASEOUS MOLECULES
THE EFFECT OF PRESSURE ON THE POSITION OF EQUILIBRIUM
Predict the effect of an increase of pressure on the equilibrium position of..
2SO2(g) + O2(g) SO3(g)
MOVES TO RHS :- fewer gaseous molecules
H2(g) + CO2(g) CO(g) + H2O(g)
NO CHANGE:- equal numbers on both sides

8. AFFECTING THE POSITION OF EQUILIBRIUM
Le Chatelier
TEMPERATURE
• temperature is the only thing that can change the value of the equilibrium constant.
• altering the temperature affects the rate of BOTH backward and forward reactions
• the direction of movement depends on the sign of the enthalpy change.
REACTION TYPE DH
INCREASE TEMP
DECREASE TEMP
EXOTHERMIC -
TO THE LEFT
TO THE RIGHT
ENDOTHERMIC +
Predict the effect of a temperature increase on the equilibrium position of...
2SO2(g) + O2(g) SO3(g) DH = - ve
moves to the LHS

9. FACTORS AFFECTING THE POSITION OF EQUILIBRIUM
CATALYSTS
Adding a catalyst DOES NOT AFFECT THE POSITION OF EQUILIBRIUM.
However, it does increase the rate of attainment of equilibrium.
This is especially important in reversible, exothermic industrial reactions such as the
Haber or Contact Processes where economic factors are paramount.
Vanadium(v) oxide catalyst used for the manufacture of sulfuric acid.  The gas inlet duct can be seen in the middle of the picture.

10. Compromise
BUT
Low temps mean low reaction rates, so we may get a higher yield but it will take a long time to get it. Not good for business.
A compromise temp, as well as the use of a catalyst will aid in speeding up the reaction to a more acceptable standard.
Temp between 700 K (425 0C) (this gives fast rate)
Overall conversion is 90% to SO3

11. More money, more SO3, but not worth it…
Also a high pressure would favour, using Le Chatelier's Principle, the formation of SO3 in the 2nd step, however its too expensive.
Reactants are compressed to 2 atm to achieve the desired flow rate in the reactor, but it is for forcing the gases more than Le Chatelier's Principle effects.
Pure O2 would drive the equilibrium to the right, however its an unnecessary expense. And there is no room on the catalyst for all that extra O2, so not enough SO3 for it to react there anyway
Low temperatures, because its exothermic, would be best for Le Chatelier's Principle, but it slows the rate too much.
Addendum:
Metal corrosion is a big issue in the manufacture of sulfuric acid.
Special alloy metals must be used to guard against excessive corrosion.
Nickel, chromium, molybdenum, copper, an silicon are the most important elements that enhance corrosion resistance of alloys.

12. The contact process LAST STEP
Problem is that not only is it slow the reaction is violent exothermic reaction
and produces a fog or mist of sulfuric acid that cannot be condensed.
In practice the SO3(g) is dissolved in concentrated sulphuric acid (that contains relatively no water)
Sulphur trioxide, from the first step, reacts with water to form sulphuric acid (in a mixture of 98% sulphuric acid and 2% water)
SO3(g) + H2O(l) H2SO4(l) (Slow and dangerous)
SO3(g) + H2SO4(l)  H2S2O7(l) disulphuric acid or oleum
H2S2O7(l) + H2O(l)  2 H2SO4(l)

14. All 3 Reactions: Summary Reaction Summary
Rx 1: S(l) + O2(g)  SO2(g) What can we do here? Answer: nothing, it goes 100% V2O5 Rx 2: 2SO2(g) + O2(g) 2SO3(g) ∆H = -196 KJ/mol Here is only place we can manipulate reaction, le Chatelier Rx 3: ACID TOWER Dangerous part of reaction as it is VERY exothermic. BOOM. H2S2O7 called pyrosulfuric acid, why? a)SO3(g) + H2SO4(l)  H2S2O7(l) (disulphuric acid/oleum) (CORROSIVE) b)H2S2O7 + H2O  2H2SO4 Waste gases need to be neutralized by?? Answer : Bases like Na2CO3
SO3
H2SO4

15. Waste Management and Environmental Impact
All three processes are exothermic, meaning energy is produced. This energy is used to generate its electricity or as a source to produce other chemicals.
Environmental Impact
The chimneys of these plants do leak out some acid that contributes to localized acid rain.
However, today they use scrubbers in the chimneys to get rid of the acid rain problem.
Can you guess what chemical is sprayed inside the chimney to reduce the acid?
Answer: Na2CO3 or other BASES.

16. The sulphuric acid industry
fertilisers
electrochemistry – batteries

17. Uses of sulphuric acid Making fertilisers (phosphate is part of NPK)
Ca3(PO4)2(s) 3H2SO4(aq)  3CaSO4(s) 2H3PO4(aq) for N, P, K
Phosphate ore
And
H2SO4(aq + 2 NH3  (NH4)2NO3
Making fertilisers (phosphate is part of NPK)

20. Uses of sulphuric acid
Acids clean metals

22. Sulfur Uses: Preservatives
Preservatives can be categorized into three general types: antimicrobials that inhibit growth of bacteria, yeasts, or molds. Sulfur Dioxide has been used in winemaking since the Romans discovered that if you burn candles made of sulfur inside empty barrels it would prevent them smelling like vinegar. Sulfur dioxide serves all three types, which is one reason why it and related compounds called sulfites are found in so many household products.