Chemistry chapter 12

• Pure Substance


  Single element or compound without impurities.
• Mixture


  Combination of two or more substances.
• Formulation


  Mixture designed for a specific use. Eg: paint , alloys, fertilisers, medicines (crude oil not a formulation because it is natural)
• Chromatography


  Technique to separate mixtures and identify substances.
• Rf Value


  Different components of a mixture move different distances in the same time.

  Rf= distance travelled by component(dye) / distance travelled by solvent.
• Stationary Phase


  Phase that remains fixed during chromatography. (the paper)
• Mobile Phase


  Phase that moves through the stationary phase. ( the solvent)
• Colour moves further if ...

  More soluble in solvent ( mp )

  Less attracted to paper ( sp )
• Chromatography required practical


  -Start line drawn in pencil(doesn't run).

  -Add solvent to beaker.

  -Add small dot of dye on start line.

  -Place end of paper in solvent with the start line above the solvent level.

  -Allow solvent to travel up paper.

  -Remove paper when solvent is near the top.

  -Calculate rf value.
• Solvent Front


  Farthest point reached by solvent in chromatography.
• Flame Test


  Method to identify metal ions in ionic compounds by flame color.
• Flame test method


  -Dip clean metal wire or damp splint in metal compound.

  -Put wire/ splint in blue Bunsen flame.

  -Observe flame colour.
• Lithium flame colour


  crimson
• Sodium flame colour


  yellow
• Potassium flame colour


  lilac
• Calcium flame colour


  orange-red
• Copper flame colour


  green
• Why would it be difficult to test a sample containing two metal ions in a flame test?


  One colour would mask the other.
• What is a precipitate?

  An insoluble solid.
• How is sodium hydroxide used to identify some metal ions?


  It forms a precipitate when added.
• Sodium hydroxide added to calcium.


  White precipitate, Ca^2+ + 2OH^1- = Ca(OH)2 [little 2] (s).
• Sodium hydroxide added to magnesium.


  White ppt, Mg(OH)2 (s)
• Sodium hydroxide added to aluminium.


  White ppt, but dissolves when more sodium hydroxide added. Al(OH)3 (s).
• Sodium hydroxide added to copper(II).


  Blue ppt, Cu(OH)2 (s).
• Sodium hydroxide added to iron(II).


  Green ppt, Fe(OH)2 (s).
• Sodium hydroxide added to iron(III).


  Brown precipitate, Fe(OH)3 (s).
• Halide ions.


  The ions formed when halogens gain electrons, eg: Cl-1, Br-1, I-1....

  Hi in a solution produce precipitates with silver nitrate solution on the presence of dilute nitric acid. (The acid removes any orge ions that may interfere with the test.)
• When silver nitrate and dilute nitric acid are added to chloride.


  White ppt, silver chloride - AgCl (s).
• When silver nitrate and dilute nitric acid are added to bromide.


  Cream ppt, AgBr (s).
• When silver nitrate and dilute nitric acid are added to iodide.


  Yellow ppt, AgI (s)
• Acid test for carbonate ions.


  Test : add acid.

  Result : bubbles of Co2.
• Barium chloride test for sulfate ions.
• Insoluble


  Substance that does not dissolve in a solvent.
• Crude Oil


  Natural mixture, not formulated for specific use.
• Chromatogram


  Visual representation of components separated by chromatography.
• Electrons


  Negatively charged particles in atoms.
• Positive Ion


  Atom that loses electrons, gaining positive charge.
• Distinctive Colors


  Unique colors produced by metals in flame tests.
• Water Purity Test


  Boiling water to check for impurities.
• Melting Point


  Temperature at which a substance changes from solid to liquid.