GCSE: OCR gateway: C2: manufacturing chemicals + acids and bases

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  • C2
    • Manufacturing Chemicals; Making Ammonia
      • The Harber Process
        • World food production depends on nitrogen fertilisers made from ammonia
        • Nitrogen + Hydrogen Ammonia
          • N2 + 3H2 2NH3
        • Optimum conditions
          • Use a catalyst made of iron
            • Increases reaction rate; collisions per second but not the percentage yield
          • Temperature around 450*c
            • Increases reaction rate
            • High temperature breaks down ammonia reducing percentage yield
          • High pressure; 200 atmospheres
            • Increases percentage yield of ammonia
          • Recycle unreacted nitrogen and hydrogen
      • What affects the cost of chemical manufacture?
        • Costs increase when pressure (plant costs) and temperature (energy costs) are raised
        • Costs decrease
          • A catalyst is used
          • Unreacted materials are recycled
          • Automation is used;less wage bills
        • Economic considerations to determine the conditions
          • Both reaction rate and percentage yield are high enough to give sufficient daily yield of product
          • Low percentage yield acceptable if reactionis repeatable and materials can be recycled
          • Optimum conditions give lowest cost rather than the fastest rate or highest yields
    • Acids and Bases
      • Alkalis and Neutralisation
        • Metal oxides and hydroxids are bases
        • Bases  soluable in water are alkalis
        • Neutralisation Acid + base = salt + water
          • Neutralisation leaves no free H+ ions
          • H+ + OH-  H2O
        • Some indicators show a sudden colour change to one pH value
        • Universal indicator shows a gradual range of colour changes as it contains a mixture of different indicators
        • In solutions all acids contain H+ ions
          • The higher the concentration of H+ ions the lower the pH
        • Alkalis contain OH- ions
      • Salts
        • Acids react with bases and metal carbonates to form salts
          • Neutralisation Acid + base = salt + water
            • Neutralisation leaves no free H+ ions
            • H+ + OH-  H2O
          • Acid + metal carbonate = salt + water + carbon dioxide
        • 2nd part of the name tells you what acid it has been made from


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