C3 (Part 2)

C3 (Part 2)

1. Analysis & synthesis

   • Titration Calculations
     • Concentration is measured in grams per decimetre cubed (g/dm3), or moled per decimetre cubed (mol,dm3)
     • If we know the mass or number of moles, in a given volume we can work out concentration
     • If we know volume of a solution and concentration we can work out the mass or moles
   • Chemical Analysis
     • Some just looks at whether it is just in a substance e.g. the ion tests
     • Others look at how much, e.g. Gas Chromatography and Mass spectometry
   • Equilibrium
     • equilibrium is when the rate of the forward reaction is equal to the rate of the backwards reaction
       • The reaction still continues but the amount of products remains constant
     • Only occurs in reversible reactions
     • The amount of reactants and products in a reversible can be changed by shifting the equilibrium
       • E.G. ICl +Cl2 --> ICl3
         • When there is plenty of Cl2 gas, more ICl3 is made
         • When there is less Cl2 gas, more ICl is made
       • Change in pressure
       • Change in Temp.
   • Haber Process
     • Makes ammonia that can be used as;
       • fertiliser
       • Explosives
       • Some cleaning fluids
     • Passed over an iron catalyst, at 200 Atmospheres. and 450 oC
     • N2 + 3H2 --> 2NH3 <--
     • The yield is only about 15% as some of the ammonia breaks back down in to N2 and 3H2
       • To try and limit this (the reverse reaction) the ammonia is cooled so it condenses, it can then be extracted
     • Optimum Conditions
       • Pressure - As the product have fewer molecules, a high pressure will give the highest amount of product
         • However a high pressure means a high cost for equipment so it can withstand the pressure, and energy to compress the gas
           • 200 Atmospheres is a good medium
       • Temp - the forward reaction is exothermic and so the lower the temp the better
         • However the rate of reaction decreases as temp. decreases and the iron catalyst becomes ineffective
           • 450 oC is a good inbetween

2. Organic Chemistry

   • Alcohols
     • Functional group = -O-H
     • Uses of alcohols
       • The smaller alcohols, Meth., Eth., Prop., react well with water to form neutral solutions
       • Many organic substances dissolve in them and so they are useful solvents
       • Ethanol is used in Alcoholic beverages
     • It reacts with sodium to form Hydrogen gas - it reacts less vigorous than Sodium in water
     • Alcohols can be oxidises by agents such as Potassium Diochromate - Oxidised Ethanol produces ethanoic acid; this is the main acid in vinegar
   • Carboxylic acids
     • Functional group = -COOH
     • They react with water to produce a solution less that pH 7
       • They also don't fully ionise in water - this means carboxylic acids are weak acids
   • Esters
     • Esters are Carboxylic acids reacted with an alcohol, in the presence of an acid catalyst
       • They have the functional group is -COO-
         • The H atom from the carboxylic acid is replaced with an alcohol
           • E.G. --> CH3 COOCH2 CH3 - Ethyl Ethanoate
     • Some smell nice and are used in fragrences
   • They can benefit society when ussed appropreately but can be harmful if abused
   • Biofuels offer an alternative to fossil fuels, but the plants they are grown from take up agriculteral land and so can cause food shortages

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