Chemistry Module 2-Haber process and salt

Chemistry Module 2-Haber process and salt

1. haber process

   • takes nitrogen and hydrogen gas to make ammonia-to make fertilisers
     • nitrogen obtained from the air
       • hydrogen comes from the cracking of oil fractions or natural gas
         • as it is reversible-not all nitrogen and hydrogen convert to ammonia
           • the hydrogen and nitrogen which dont react are recycled
             • uses a pressure of 200 atmospheres
               • 450 degrees
                 • and iron catalyst
   • conditions
     • high pressure increases percentage yield
       • high temperatures favour reverse reaction-decreases percentage yield
         • 450 degrees is optimum to give a fast reaction with sufficiently high percentage yield
           • iron catalyst speeds up rate of reaction,but does not change percentage yield
             • doesnt affect equilibrim
             • without catalyst-temperature would increase but this decreases percentage yield
   • factors that effect cost of production
     • price of energy-higher temperature the higher cost of energy
       • cost of raw materials-unreacted materials recycle to keep costs low
         • labour costs-automation cuts running costs by reducing the number of people involved
           • plant cost- high pressure high cost of equipment
             • rate of production-catalyst used to reduce time and cost of production
               • increase in production rate has to balance the cost of buying the catalyst in the first place
                 • and replacing anything that gets lost
     • economic considerations
       • rate must be high enough to give a sufficient daily yield
         • optimum conditions used to give lowest cost rather than highest yield
           • low percentage yield accept if recycled products used

2. to test a reversible reaction

   • reactants change into products at the same time as products change into reactants
     • dynamic equilibrium
       • copper sulfate crystals(hydrated) heated
         • gradually water from blue copper sulfate evapourated
           • then condensed in the test tube
             • became white because it was unhydrated
               • poured water back in to test tube and it turned back to blue copper sulfate crystals

3. salt

   • mined by pumping hot water underground
     • the salt dissolves and the salt solution is forced to the surface by the pressure of water
       • solution used for electrolysis
         • this is solution mining
           • mining
             • this method of extraction leaves insoluble impurities-reddish clay
               • used on roads when cold
                 • sea water
                   • underground deposits when ancient seas evaporated.
                     • or heating seawater in the sun-starts to crystalise
             • when finished must fill in holes in the ground
               • if not land could collapse and slide into holes-subsidence
   • electrolysis of brine
     • used to manufacture chlorine from salt
       • gives hydrogen,chlorine and sodium hydroxide
         • hydrogen= -ve cathode
           • chlorine gas= +ve anode
             • sodium hydroxide=formed from ions left in solution
               • half equations
                 • anode
                   • 2CL- - 2e- = Cl2
                     • oxidation
                       • chlorine atoms move in to chlorine gas
                 • cathode
                   • 2H+ + 2e- = H2
                     • reduction
                       • hydrogen move into hydrogen gas
                 • sodium hydroxide removed as a liquid
                   • spectator ion
     • chlor-alkali industry
       • electrolysis of brine is done by the chlor-alkali industry
         • hydrogen gas is used to make ammonia and margarine
           • chlorine used to disinfect water to make plastics,solvent or hydrochloric acid
             • sodium hydroxide- used to make soap, or reacted with chlorine to make household bleach
               • means lots of products and jobs for the industry
   • uses of salt
     • sterilisation and disinfecting
       • preservation of food
         • soap industry
           • produce hydrogen,chlorine and sodium hydroxide by electrolysis
             • glass making
               • paper making

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