Chemical AnalysisChemical AnalysisL.O: L.O: To know how to analyse and identify metal ions in unknown substances

Starter: Think of a few examples of why chemical identification may be needed by:Environment scientists Forensic Scientists Health Care Scientists

Forensic scientists have to Forensic scientists have to identify lots of mystery identify lots of mystery substances. (explosives, drugs, substances. (explosives, drugs, soil in shoes) The problem is soil in shoes) The problem is many substances look very many substances look very similar!similar!

What could this be?

Environmental scientists might Environmental scientists might have to identify pollutantshave to identify pollutants

Healthcare scientists might have Healthcare scientists might have to identify drugs in athletes, to identify drugs in athletes, substances in dialysissubstances in dialysis

Spot the mistakesSpot the mistakes

Lithium ion LiLithium ion Li++

Copper II ion CuCopper II ion Cu++

Magnesium ion MGMagnesium ion MG2+2+

Potassium ion PPotassium ion P++

Oxygen ion OOxygen ion O2-2-

Chlorine ion ClChlorine ion Cl--

Helium ion HeHelium ion He++

Nitrogen ion NNitrogen ion N3+3+

Iron II ion FeIron II ion Fe2+2+

Methods of Methods of

Analysis Analysis Chemists are often asked to identify the ions

present in a compound. Remember the instrumental methods in C2? Paper

chromatography, Gas Chromatography, Mass Spectrometry?

Disadvantages of Using Instrumental Methods

• Usually Expensive

• Need Special Training

• Results usually need to be compared to already known specimens

Advantages of Instrumental methods

• Highly accurate

• Much Quicker

• Enable small quantities of chemicals to be analysed

We are going to perform some human tests today. What are the advantages of doing these over instrumental tests?

Identifying Metal Identifying Metal

IonsIons Add sodium hydroxide to the solution

Dirty Green Precipitate = Iron II

Brown / Orange Precipitate = Iron III

Light Blue Precipitate = Copper II

White precipitate = Could be Calcium, Magnesium, Aluminium

Add Excess Sodium Hydroxide

White precipitate Disappears

White precipitate doesn’t Disappear

Aluminium

Calcium or Magnesium

Flame Tests

Lithium = Crimson

Sodium = Orange

Potassium = Lilac

Calcium = Brick Red

Barium = Light green

Identifying Metal Identifying Metal

IonsIons Add sodium hydroxide to the solution

Dirty Green Precipitate =

Brown / Orange Precipitate =

Light Blue Precipitate =

White precipitate = Could be Calcium, Magnesium, Aluminium

Add Excess Sodium Hydroxide

White precipitate Disappears

White precipitate doesn’t Disappear

Flame Tests

Lithium =

Sodium =

Potassium =

Calcium =

Barium =

Potassium

Barium Sodium Calcium Lithium