SC25 - Qualitative Analysis: Test for Ions ✓

(Bright) Red [Lith-le red riding hood]

Yellow

Lilac P̶u̶r̶p̶l̶e̶.̶ ̶A̶H̶H̶H̶H̶H̶ ̶I̶’̶M̶ ̶S̶O̶R̶R̶Y̶ ̶O̶K̶ ̶O̶K̶ ̶I̶T̶S̶ ̶N̶O̶T̶ ̶P̶U̶R̶P̶L̶E̶

Orange-red

Blue-Green

• Light a Bunsen burner to a strong blue flame • Pick up a sample of the substance with a small wire loop • Hold the sample into the edge of the flame and observe the colour

• It has a high melting point and so won’t melt • It is inert and so won’t react It doesn’t produce/affect a flame colour

• It is cheaper • However, it produces a light orange flame that could affect the results

• When a solution containing the metal ions creates a flame and the light intensity is measured by a computer. • This allows it to have quantitative and comparable data

• Sensitivity: Much smaller sample sizes can be used • Accuracy: They give results closer to the true value • Speed: They occur with more quickness [look at me defining speed like a pro]

• It shows the light intensity produced by metal ions in different concentrations of solutions • It is created by using standard solutions of known concentrations • This allows data comparison to be accurate

They can separate the light produced into a spectrum of different colours (wavelengths) of light

• Metal ions each produce their own unique combination of different wavelengths of light • This different colours are the emission spectrum of an ion and can be used to identify ions • Together, these different colours will produce the one colour seen in the flame test

• A few drops of sodium hydroxide are added to a solution containing metal ions • The metal and the hydroxide will react to form metal hydroxide • This will be insoluble and form a precipitate of a colour that can be used to identify the metal

Green

Brown

Blue

White

White

• Both calcium and aluminium ions will produce a whit precipitate when reacted with sodium hydroxide. • Thus, a distinguishing test is required In this case, excess sodium hydroxide is added • For aluminium ions, this causes the precipitate to eventually turn colourless

• Dilute sodium hydroxide solution is added which produces ammonia gas • Ammonia gas has a characteristic sharp smell but a confirmatory test is needed to be sure • Ammonia gas turns damp red litmus paper blue

• Add dilute hydrochloric acid to the sample If it does contain a carbonate, this will cause carbon dioxide to be produced • This will cause effervesence • To make sure this is carbon dioxide, bubble the gas produced through limewater • If carbon dioxide is present, limewater will turn colourless to cloudy.milky

• Add some dilute hydrochloric acid to the solution • Then add barium chloride If sulfate ions are present, this will produce a white precipitate of (insoluble) barium sulfate

To remove any carbonate ions and therefore eliminate the chance of a false positive result