Chem topic 8

• impure and Pure substance in chemistry

  A pure substance is a single Element or compounds that is not mixed with any other substances, and melts and boils at specific temperatures. Impure substances are mixed and melt/boil at a range if temperatures
• Test for purity


  Melt the substance or boil it and compared the melting or boiling point to what it would be if it was pure.

  The purer it is, the closer the melting point is to a pure one
• Formulation


  A mixture that has been designed as a useful product.
• Making a formulation 


  the quantity of each component is carefully measured to ensure it has the desired properties.
• Eggs of formulations

  Fuel cleaning agent paint medicine alloy fertiliser food
• Rf calculation 


  Distance moved by substance/distance moved by solvent
• Identifying compounds using Rf value


  Different compounds will have different Rf values so you can do chromatography and compare the value to a database
• Pure and impure - chromatography


  Impure substances will form many dots, whilet pure substances will only have one spot
• Stationary and mobile phase


  The stationary phase is the dot and ten mobile The stationary phase is the dot whilst the mobile phase is the olfent
• Test for hydrogen


  hold a burning splint near the open end of a test tube, there should be a squeaky pop and it should burn
• Test for chlorine


  Damp litmus papers Is bleached and turns white
• Test for co2

  Co2 bubble into limewater or shaken it turns cloudy/milky
• Flame tests to identify cations

  Lithium - crimeon flame

  sodium - yellow flame

  Potassium. - Liliac flame

  Ca2+ - orange red flame. Cu2+ - produces green flame
• How can metal hydroxides be u to identify metal ions 


  Adding hydroxide to it.
• METALOHs that turn white


  Al Ca Mg if NaOH is added, Al precipitates dissolves in excess sodium solution into coloured compound
• Metals that for, coloured precipitate When NaOH is added

  Cu2+ Fe2+ Fe3+
• Cu2+ 


  blue
• Fe2+


  green
• Fe(III)


  Brown
• Carbonates react with dilute acids to form 


  co2 gas which can be tested for using limewater
• Anion test -co3


  Carbonate react with dilute acid releasing co2 gas

  place carbonate and dilute acid in test tube, connect to tube with limewater, limewater turns milky
• Halide test


  Cl- Br- I

  Mix halide with nitric acid and then silver nitrate, turns into silver halide.
• agcl precipitate colour


  white
• Brcl precipitate colour


  Cream
• Icl colour


  Yellow
• Sulfate tests


  Add dilute hcl and bacl2, SO4forms A precipitate with BaCl2 in presence of dilute hydrochloride acid
• Instrumental methods and advantages


  Test that use machines and identify elements and compounds. Advs include more accurate, faster, sensitive
• Flame emission spectroscopy


  Sample placed into flame, lights given out is passed through spectroscope, which outputs line spectrum which csn be sued to identify cations