tests and reagents

  • Created by: Lndavies
  • Created on: 05-05-19 17:44
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  • Tests and reagents-
    • Group 2-
      • Reactions with hydroxide ions from least to most soluble- magnesium, calcium, strontium and barium
      • Reaction with sulfate ions from most to least soluble, magnesium, calcium, strontium and barium.
      • calcium hydroxide and magnesium hydroxide are used to neutralise acid.
      • calcium oxide and calcium carbonate remove flue gasses such as sulfur dioxide.
      • flame tests- calcium will go brick red, strontium will go red and barium will go pale green.
    • Halogens-
      • Reachions with sulfuric acid- NaF and NaCl. HF and HCl are formed the reaction goes no further because they aren't strong reducing agents.NaBr, first HBr gasses are formed then Br2 fumes( orange) and SO2 and H2O. NaI, HI is formed then reduced H2SO4 to SO2,H2S and solid iodine.
      • silver nitrate- silver nitrate with dilute nitric acid and halogens forms- fluorine- no ppt .chlorine- white ppt. bromine- cream ppt. iodine- yellow ppt.
        • when ammonia is added- chlorides white ppt dissolves in dilute ammonia. bromines cream ppt dissolves in concentrated ammonia and iodides yellow ppt doesn't dissolve in concentrated ammonia
      • halogens displace less reactive halide ions from solution. chlorine displaces bromide which forms orange solution and iodide which forms brown solution and bromine displaces iodide forming brown solution
      • carbonates- hydrochloric acid can detect carbonates as you will see effervescence and cloudy limewater.
    • Period 3
      • reactions with water- sodium reacts more vigorously with cold water producing fizzing of hydrogen and a strongly alkali solution. magnesium react very slowly with cold water but very fast with steam
      • reaction with oxygen- Na= vigorously, Mg= vigorously, Al= slow, Si=slow, P= spontaneously combusts and S burns steadily
    • transition metal titrations
      • aqueous potassium manganate is the main oxidising agent, it needs strongly acidic conditions to be reduced.
    • Metal-aqua ions
      • adding OH ions to solutions produced insoluble metal hydroxides
      • metal hydroxides that can act as an acid or a base are amphoteric. such as aluminium hydroxide.
      • reactions with sodium hydroxide- aluminium hydroxide will form precipitate but will then dissolve due to its amphoteric nature.
      • reactions with ammonia- copper hydroxide, ppt will form but then dissolve due to ligand substitution
      • sodium carbonate- solutions containing Al3+ or Fe3+ bubbles will form. whereas Fe2+ wont produce bubbles.
    • Alkenes-
      • bromine water test- bromine water is used to test for unsaturation, the bromine water decolourises as electrophilic addition takes place
    • alcohols-
      • ethanol is heated with  concentrated sulfuric acid or H3PO4 to produce ethene.
      • reflux- heating ethanol with acidified potassium dichromate, acidified by sulfuric acid. it is first turned into an aldehyde then carboxylic acid by heating it. reflux means heating a reaction without losing volatile solvents.
    • aldehydes + ketones-
      • fehlings solution and benedicts- blue solution turns brick red ppt with added with an aldehyde.
      • tollens reagent- made up of silver nitrate, dilute sodium hydroxide and ammonia solution. when added with an aldehyde a silver mirror forms.
    • amines
      • you can reduce a nitrile to primary amine. using lithium aluminium hydride (LiAlH4) with dilute acid .
      • aromatic amines are made by reducing nitro compounds. you heat it with tin metal, concentrated hydrochloric acid and sodium hydroxide

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