Production of ammonia, alcohols, carboxylic acids and Esters

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  • Production of ammonia, alcohols, carboxylic acids and Esters
    • The Haber process
      • Reversible reactions don't go to completion, but can still be useful
      • Used to manufacture ammonia
        • Raw materials used are -nitrogen (from fractional distillation of air) & -hydrogen (from natural gas and steam)
      • Purified nitrogen & hydrogen are passed over an iron catalyst at a high temperature (about 450 degrees C) & high pressure (about 200 atmospheres)
      • Some of the nitrogen and hydrogen react to form ammonia which can break back down into it's reactants again.
      • These reaction conditions are chosen to produce a reasonable yield quickly. Even so only some atoms react together
    • Closed systems
      • No reactants are added & no products are removed
      • When a reversible reaction happens in a closed system, an equilibrium is achieved
      • Equilibrium = Both reactions occur at same rate in each direction
      • Relative amounts of all reacting substances at equilibrium depend on conditions of reaction
    • Changing reaction conditions
      • In an exothermic reaction: Temperature raised = yield decreases & Temperature lowered = yield increases
      • In an endothermic reaction: Temperature raised = yield increases & Temperature lowered = Yield decreases
      • In gaseous reactions: increase in pressure favours reaction that produces least number of molecules
    • Alcohols
      • Carbon based molecule
      • Functional group = OH
      • Methanol, Ethanol & Propanol = first 3 members of homologous series
      • -Dissolve in water to form neutral solutions
      • -React with sodium to produce hydrogen
      • Burn in air
      • Used as fuels & solvents
      • Ethanol can be oxidised to ethanoic acid by chemical oxidising agents or microbial action.
        • Ethanoic acid is main acid in vinegar
      • CH2 is added for each next member of homologous series
    • Carboxylic Acids
      • carbon-based molecules
      • Functional group = COOH
      • Dissolve in water to form acidic solutions
      • React with \carbonates (e.g. sodium carbonate) to produce CO2
      • React with alcohols (in presence of acid catalyst) to form Esters
      • Carboxylic acids don't ionise (dissociate) fully in water, so they're called weak acids
      • Aqueous solutions of weak acids have higher pH than aqueous solutions of strong acids with same concentration
      • Methanoic acid - COOH, Ethanoic acid - CH3COOH, Propanoic acid - CH3CH2COOH
    • Esters
      • Alcohols & Carboxylic acids react to form Esters.
      • When ethanol &ethanoic acid react the ester formed is ethyl ethanoate.
        • Ethyl ethanoate = CH3COOC2H5
      • Functional group = COO
      • Volatile compounds (low boiling points)
      • Distinctive smells, so are used in perfumes and foods

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