Unit C5

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  • Unit C5 quantive analysis
    • acids and akilies
      • hydrocloric acid = HCl
      • nirric acid HNO3
      • sulfric acid H2SO4
      • soudium hydroxide NAOH
      • an acid with a lower ph is stronger than an acid with a higher ph
    • titrations
      • these are used to find the contations of an unknown acid
      • this is found using a known contraition and adding a indicator for example phenolthaline that will change immediately
      • once you have found the amount you must convert it into decimetres cubed to find the concentration
      • titration equation
        • work out the hydrogen to hydroxide ratio
          • then work out the amount yuou need to nutrlise the other substance baised off the ration convert this to decimters
            • then use this equation amount of moles / volume to get concentration
      • neutralisation is H+ + OH-____>H2O
      • important equation conc=amount of moles /vol
      • single change indicators should be used as they give a more clear colour change
    • empirical formulae and % composition
      • how to do a empirical formulae  equation divide the amount by its MR to get the to number then get the smallest number say you divide h20 with 50% oxygen and 25% hydrogen so 50/1 = 50 25/ 16 =1.5625 you would divide both of these numbers by 1.5625 to get the number then you work this out in a ratio  for water 2 hydrogen to one oxygen giving H2o
        • this is the simplest number ratio for the chemical for example glucose is CH2O
      • the % com is how much one substance is of an element
        • for example find the % com of oxygen in 40n g of MgO so you do 16/40x100 to get 40%
    • solutions and concentrations and quantive analysis
      • solution = a solute dissolved in a solvent
      • concentration =the strength of a substance the amount of solute in a given volume of solvent
      • a decimetre is the standard volume of measurement when dealing with concentrations
        • it is equivalent to 1000 cm cubed
      • the contrition of a solution is measured in mols per dm cubed  or in G/dm3
      • knowing about mols is important as it helps with things like making orange juice or baby milk
    • gas volumes
      • as many reaction HAVE A GAS AS A PRODUCT IT NEEDS TO BE MESSURED SO IOLUMES AS THIS IS TYHE EAISYEST WAY TO DO THIS
      • to measure this you can use a upturned cylinder or burette but for the most accurate results you should use a gas syringe
      • thwe amount of gas produced will be decided by the limiting factor so the lower the limiting factor the less gas will be produced
      • to work out gas molarity you need to replace molar mass with 24dm 3
    • equilibrium and the contact proses
      • this happens during reversabel reactions
        • it means THE FOWARD REACTION IS EQUAL TO THE BACIKWARDS REACTION
          • this can happen because it is not a closed system at first the rate of the forward decreases and they backward increases and they become equal
            • adding  a extra product increasing temperature pressure all effect equilibrium
      • this process is used to create sulphuric acid
        • first you start with these raw materials
          • water sulphur and oxygen
            • stage 2= suphur + oxygen ----> sulphur dioxide
              • stage two more oxygen ids added to make the substance sulphur trioxide this is a reversible reaction
          • you also need 450oc of heat a vanadium oxide catalysis and atmospheric pressure
            • a change in any of these may change the equilibrium
    • precipitation reactions and ionic equations
      • most precipitation reactions involve ions form one solution reacting with ions from another solution
      • chlorine reform a white precipitate bromine form A cream precipitate and iodine forms a yellow precipitate
      • precipitation reactions are extremely fast
      • you cab test form sulphate ions using barium chloride
  • this is because it is more ionsing this is strength of the acid this has nothing to do with concentration
    • an acid with a lower ph is stronger than an acid with a higher ph

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