Sulfuric Acid

 P Manufacture of paper  Di Manufacture of drugs  Di Manufacture of dyeshas a...  PManufacture of pigments  HHousehold  D Detergent (manufacture )in...  Beats As the electrolyte in car batteries  Per Petroleum refining  MinuteMetallurgical processes

 75% of the Sulfuric Acid that is produced is used to make fertilisers such as  Superphosphate  Ammonium sulphate and  Ammonium phosphate.

 Rock phosphate contains insoluble Calcium Phosphate. What is the formula for Calcium Phosphate???  Ca 3 (PO 4 ) 2  To be made available to plants it needs to be converted to a soluble form:  Ca 3 (PO 4 ) 2, (s) + 2H 2 SO 4 (l) + 4H 2 O  Ca(H 2 PO 4 ) 2 (s) + 2CaSO 4 2H 2 O (s)

 Australia has substantial rock phosphate resources, especially in Queensland  Australian companies usually import rock phosphate from North Africa. WHY?  Cheaper

 H 2 SO 4 (l) + H 2 O (l)  HSO 4 - (aq) + H 3 O + (aq) The Ka for this reaction is very high  HSO 4 - (aq) + H 2 O (l)  SO 4 2- (aq) + H 3 O + (aq) The Ka for this reaction is small  These reactions are EXTREMELY exothermic. Because of this it is important to add acid to the water and not the other way around.  The reaction is so exothermic that water becomes steam and causes the solution to splutter, causing serious injury.

 Sulphuric acid acts as a catalyst in the following reactions: C 1 2 H 22 O 11 (s) (with H2SO4)  12C (s) + 11H 2 O (l)  Is this a condensation reaction, hydrolysis reaction or neither?

 CuSO 4 5H 2 O (s)  CuSO 4 (s) + 5H 2 O (l)  Sulphuric acid can even be used as a dehydrating agent for gases by bubbling them through the sulphuric acid.  However, these gases cannot be bases (i.e. NH 4 ) or reductants. Why?

 What health implication might there be for sulphuric acid being such a strong dehydrating agent?

 If sulfuric acid is spilt on the skin, wash with running water (wink wink, hint hint)  If there is a large amount of sulfuric acid, first wipe it off quickly

 A very strong oxidant, especially when hot.  H 2 SO 4 can be reduced to SO 2 S or H 2 S :  Zn (s) + 2H 2 SO 4 (l)  ZnSO 4 (aq) + H 2 O (l) + SO 2 (g)  3Zn (s) + 4H 2 SO 4 (l)  3ZnSO 4 (aq) + 4H 2 O (l) + S (s)  4Zn (s) + 5H 2 SO 4 (l)  4ZnSO 4 (aq) + 4H 2 O (l) + H 2 S (g)  However, when zinc reacts with dilute H 2 SO 4 :  Zn (s) + H 2 SO 4 (l)  ZnSO 4 (aq) + H 2 (g)  For each of the reactions above, identify the oxidation numbers of Sulfur.

 The production of H 2 SO 4 usually follows the following process: S  SO 2  SO 3  H 2 SO 4  This is know as “The Contact Process”

 Combustion of sulphur recovered from natural gas and crude oil  SO 2 formed during the smelting of sulphuric ores of Cu, Zn or Pb  It can be mined directly. This is not necessary in Australia

 If solid sulfur is the starting point it is made molten and then sprayed under pressure into a furnace.  It will then combust in air to produce SO 2  The high surface area of molten S results in a very fast combustion reaction.  S (l) + O 2(g)  SO 2 (g) Δ H = -297 kj mol -1  Temperature may reach 1000°C so SO 2 needs to be cooled

 SO 2 is converted to SO 3 with the use of the V 2 O 5 catalyst.  2SO 2 (g) + O 2(g) (with V 2 O 5 )  2SO 3 (g) Δ H = -197 kj mol -1  Where does this reaction occur? Well, thanks for asking, it occurs in a.....

 SO 2 is mixed with air and passed through trays containing loosely packed porous pellets of the catalyst V 2 O 5  Because the reaction is so exothermic it must continually be cooled  The temperature in the converter is maintained at °C and a pressure of 1 atmosphere  Nearly complete conversion from sulphur dioxide to sulphur trioxide is achieved. SO?

 Use Le Chatelier’s principle to determine what temperatures and pressure is desired for this reaction.  Also, would excess reactants be employed?  Excess products? Why/Why not?  What about dilution?

 Temperature: Because the reaction is exothermic Le Chatalier predicts the reaction will become more product favoured when the temperature is decreased  Because the generation of products decreases pressure, an increase in pressure will push the reaction forward  By supplying excess reactants the system will try to re-establish equilibrium by getting rid of those reactants. This will also push the reaction forward.

 What factors will increase the rate of reaction?  High Temperature  High Pressure  The use of a catalyst

 In most instances both a product favoured reaction and a speedy reaction desire the same factors.  Excess oxygen is used as the excess reactant  Even though increased pressure increases the rate of reaction and pushes it forwards, manufacturers do not bother as high yields are achieved without this costly addition.  Le Chatelier dictates that a low temperature will push the reaction forward. However, the rate of reaction will slow with reduced temperature. What to do?!

 Luckily, the catalyst saves the day by making lower temperatures viable.  The effect of the catalyst is maximised by spreading it over trays which increases the surface area.  The catalyst can become ‘poisoned’ and rendered ineffective by dust. Therefore the air and sulphur dioxide pass through electrostatic precipitators before they enter the converter.

 Absorption of SO 3  SO 3 (g) + H 2 O (l)  H 2 SO 4 (aq) Δ H = -130 kj mol -1  Direct reaction with water is very exothermic which results in the formation of steam. Sulfuric acid as a gas is very difficult to collect so an absorption tower is used instead:  H 2 SO 4 (aq) + SO 3 (g)  H 2 S 2 O 7 (l) This product is called oleum  Very little reactant is left. Oleum is then mixed with water:  H 2 S 2 O 7 (l) + H 2 O (l)  2H 2 SO 4 (l)  Sometimes the reactions occur simultaneously:  H 2 SO 4 (aq) + SO 3 (g) + H 2 O (l)  2H 2 SO 4 (l)

 Plants built after 1970 use ‘double desorption’ processes. The unreacted SO 2 is passed back through the catalytic converter. This increases efficiency from 98% to 99.6%  SO 2, SO 3 and H 2 SO 4 emissions are continuously monitored.  H 2 SO 4 mist is minimised by controlling the operating temperature of the absorber, gas flow rates and concentrations.  H 2 SO 4 has a high boiling temperature of 290°C and a low vapour pressure. There is no appreciable air pollution problem with its storage, handling and shipping.  Cooling water is usually recycled

 Improvements to conversion have occurred by adding small amounts of cesium to the V 2 O 5 catalyst.  This has increased efficiency and allows the reaction to occur at even lower temperatures.  Unfortunately the presence of cesium increases the cost of the catalyst by three times.  Spent Vanadium is slightly toxic so it needs to be recovered from ‘poisoned’ catalyst before the catalyst is disposed of in landfill.

 “The ‘Contact Process’ actually reduces pollution!”  Prove or disprove this statement.  2 minutes 2 reasons

 By using the sulphur by products of other reactions it prevents these pollutants escaping into the atmosphere.  This helps to prevent acid rain. Yay!  More energy is produced in the process than is used by it. Another yay!  This energy is recycled by the plant and can even be sold to other plants for use in chemical manufacture.  Sometimes the energy is used to produce ‘green’ electricity.

 Transport procedures need to be in place for loading and unloading  H 2 SO 4 is highly corrosive. It is a strong dehydrating agent. It can burn eyes and skin severely. It can cause blindness and 3 rd degree burns.  Sulfuric acid mist can cause problems such as pulmonary oedema (fluid in the lungs).  Sulphur dioxide and sulphur trioxide are respiratory irritants, damage plants and contribute to acid rain.  Oleum is a highly corrosive, oily liquid, that produces SO 3 fumes. These fumes can build up and accidental release procedures need to be in place.  Work areas must be well ventilated and employees must wear protective clothing.  Acid spills are contained using materials such as earth, clay or sand, then slowly diluted with water before being neutralised with a base (usually CaCO 3 or Na 2 CO 3 )

 What does “P DiDi has a PhD in Beats Per Minute” stand for?  What is the name, location of and formula for the catalyst that is used?  Vanadium Pentoxide, Converter, V2O5  What is the chemical formula for Oleum? H2S2O7  Which reaction occurs in the ‘converter’? SO2 to SO3  What two reactions need to occur for the adsorption of sulfur trioxide?  SO3 + H2SO4  H2S2O7  H2S2O7 + H2O  2H2SO4  How is sulfur converted to sulfur dioxide?  Molten sulfur is sprayed into the air  Write the formula for the production of superphosphate

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 From Chapter 22 Answer:  Q 2, 3, 5, 6, 7, 8, 9, 10, 11, 13, 15  You will have a SACT test on sulfuric acid and its production next Monday, so get studying!