3. Chemical analysis

    Cards (14)

    • Pure substances
      • single element or compound not mixed with any other substances
      • Melt and boil at specific temperatures
      • Melting and boiling pointing data can be used to distinguish pure substances from mixtures
      • Pure substances have nothing added to it so it’s unadulterated and in its natural state
      • Eg. Pure milk
    • formulations
      • a mixture that has been designed as a useful product
      • complex mixtures in which each chemical has a particular purpose
      • mixing components in carefully measures quantities to ensure that the product has the required properties
      • eg. fuels , cleaning products , paints , medicines , alloys , fertilisers and foods
    • chromatography
      • RF values = ratio of the distance moved by a compound (centre of spot from origin) to distance moved by solvent
      • distanced moved by substancedistance moved by solvent \frac{dis\tan ced\ moved\ by\ subs\tan ce}{dis\tan ce\ moved\ by\ solvent\ }
      • Different compounds have different Rf values in different solvent which can be used to help identify the compounds
      • Mixtures - Separate into different spots depending on solvent
      • Pure compound - produce a single spot in all solvents
    • test for hydrogen
      • use a burning splint held at the open end of a test tube of the gas
      • hydrogen burns rapidly with a pop sound
    • test for oxygen 

      • uses a glowing splint inserted into a test tube of the gas
      • the splint relight with oxygen
    • Test for carbon dioxide
      • aqueous solution of calcium hydroxide (lime water)
      • When carbon dioxide is shaken with or bubbled through lime water
      • The limewater turns milky / cloudy
    • test for chlorine
      • use litmus paper
      • damp litmus paper is put into chlorine gas
      • the litmus paper is bleached and turns white
    • flame tests
      L ook C an S ophie Y ell P oignantly L ouder C ause O liver C an G o
      • Lithium - crimson flame
      • Sodium - yellow flame
      • potassium - Lilac flame
      • calcium - orange red flame
      • copper - green flame
      if a sample containing a mixture of ions is used some flame colours can be masked
    • Metal hydroxides
      • sodium hydroxide can be used to identify some metal ions
      • Aluminium , calcium , magnesium —> white precipItates
      -aluminium hydroxide precipitate dissolves in excess sodium
      • copper II —> blue preCipitate
      • Iron II —> green precipitate
      • Iron III —> brown precipitate
      Eg. Calcium nitrate + sodium hydroxide —> sodium nitrate + calcium hydroxide
    • carbonate
      • react with dilute acids to form carbon dioxide
      • carbon can be identified with lime water
    • Halides
      • halide ions in solution produce predicates with silver nitrate solution in the presence of dilute nitric acid
      • silver chloride —> white
      • silver bromide —> cream
      • silver iodide —> yellow
    • Sulfates
      • sulphate ions in solution produce a white precipice worth barium chloride solution in the presence of dilute hydrochloric acid
    • instrumental methods
      • elements and compounds identified using instrumental methods
      • accurate , sensitive and rapid
    • flame emission spectroscopy
      • example of an instrumental method used to analyse metal ions in solutions
      • sample put into a flame and the light given out is passed through a spectroscope
      • the output is a line spectrum that can be analysed to identify the metal ions in the solution and measure their concentration
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