Do Now:

Do Now:

Do Now: Complete the empirical formula worksheet. Ask someone that was in P5 Science yesterday for help if you dont understand. Flame Tests And Precipitation Reactions. To be able to describe: Flame tests to identify metal ions. Lithium, Sodium, Potassium, Calcium, Barium. Precipitation reactions: The precipitates formed when different ions react with Sodium Hydroxide. Flame Tests: Describe flame tests to identify metal ions. http://www.youtube.com/watch?v=rEWLFH-QpWE Method: dip a clean flame test loop in the sample solution hold the flame test loop at the edge of a Bunsen burner flame observe the changed colour of the flame, and decide which metal it indicates clean the loop in acid and rinse with water, then repeat steps 1 to 3 with a new sample

Flame Tests Describe flame tests to identify metal ions. metal barium calcium copper lithium sodium potassium flame test colour pale green yellow-red green-blue red orange lilac Precipitation Reactions Sometimes when two solutions are mixed, they react to form an insoluble solid product. The insoluble solid product is called a precipitate. You can spot a precipitate because the mixture goes cloudy. For example, mixing solutions of lead nitrate and sodium chloride produces a yellow precipitate of lead chloride.

lead nitrate Pb(NO3)2 (aq) + sodium chloride lead chloride + sodium nitrate + 2NaCl (aq) PbCl2 (s)

+ 2NaNO3 (aq) Metal Ion Al2+ Reacts With NaOH Colour of PPTE White Ca2+ NaOH White Mg2+ NaOH White Cu2+

NaOH Blue Fe2+ NaOH Green Fe3+ NaOH Brown If you get a white precipitate: Add more sodium hydroxide solution, aluminium precipitate will dissolve. If the white precipitate does not dissolve then the metal ion is calcium or magnesium. These can be distinguished using a flame test (magnesium ions have no flame colour). What colour would we get for a flame test for Calcium ions? aluminium chloride + sodium hydroxide AlCl3(aq)

+ 3NaOH(aq) The ionic equation is aluminium hydroxide + sodiumchloride Al(OH)3(s) Al3+(aq) + 3OH-(aq) + 3NaCl(aq) Al(OH)3(s) Aluminium hydroxide is white. calcium chloride + sodium hydroxide CaCl2(aq) + 2NaOH(aq) The ionic equation is

calcium hydroxide + sodium chloride. Ca(OH)2(s) Ca2+(aq) + 2OH-(aq) Calcium hydroxide is white. + 2NaCl(aq) Ca(OH)2(s) magnesium chloride + sodium hydroxide MgCl2(aq) + 2NaOH(aq) The ionic equation is magnesium hydroxide + sodium chloride Mg(OH)2(s) Mg2+(aq) + 2OH-(aq)

+ 2NaCl(aq) Mg(OH)2(s) Magnesium hydroxide is white. copper(II) chloride + sodium hydroxide copper(II) hydroxide + sodium chloride CuCl2(aq) + 2NaOH(aq) The ionic equation is Cu(OH)2(s) Cu2+(aq) + 2OH-(aq) + 2NaCl(aq) Cu(OH)2(s)

iron(II) chloride + sodium hydroxide FeCl2(aq) + 2NaOH(aq) The ionic equation is iron(II) hydroxide + sodium chloride. Fe(OH)2(s) Fe2+(aq) + 2OH-(aq) + 2NaCl(aq) Fe(OH)2(s) Iron(II) hydroxide is green. iron(III) chloride + sodium hydroxide FeCl3(aq) +

3NaOH(aq) The ionic equation is iron(III) hydroxide + sodium chloride Fe(OH)3(s) Fe3+(aq) + 3OH-(aq) Iron(III) hydroxide is brown. + 3NaCl(aq) Fe(OH)3(s) Applications: Most precipitation reactions are very fast reactions that occur between ions. This makes them very useful for identifying specific ions based on the type of precipitate formed. Precipitation reactions have a number of other uses: production of coloured pigments

for paints and dyes removal of toxic chemicals from water separation of reaction products. A lead iodide precipitate. Reactions of Carbonates All metal carbonates react with dilute hydrochloric acid to produce Carbon Dioxide. Write the reactions of Calcium Carbonate, Sodium Carbonate and Magnesium carbonate with Hydrochloric acid: Remember to write word then balanced symbol equations check, the group numbers to help you to balance the equations. Carbon dioxide precipitates Limewater: Can you remember the reaction for this (C1 Limestone cycle).

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