CHEMICAL ANALYSIS Flashcards
What is a pure substance?
Something that only contains one element or compound
How do pure substances and melting/boiling points relate?
Pure substances melt or boil at a specific temperature
What happens to the boiling and melting point if a substance is impure?
Decreases melting point
Increases boiling point
What are formulations?
Useful mixtures with a precise purpose
What are examples of formulations?
Medicine
Paint
What is the mobile phase in chromatography?
Where the molecules can move (liquid or gas)
What is the stationary phase in chromatography?
Where the molecules can’t move (solid or really thick liquid)
How do you test for chlorine?
Chlorine bleaches damp litmus paper turning it white (may turn red at first because acidic)
How do you test for oxygen?
Put a GLOWING splint inside a test tube containing oxygen and it will relight
How do you test for carbon dioxide?
Bubbling carbon dioxide through an aqueous solution of calcium hydroxide (limewater) will turn the solution cloudy
How do you test for hydrogen?
Place a LIT splint into a test tube containing hydrogen and a ‘squeaky pop’ sound will be made
How do you test for carbonate ions?
Put substance in test tube and at drops of dilute acid (using pipette)
Connect the test tube to test tube of lime water
If carbonate ions are present, carbon dioxide will be released and turn the limewater cloudy
How do you test for sulphate ions?
Add a couple of drops of dilute hydrochloric acid and then barium chloride solution
If sulphate ions are present, a white precipitate of barium sulphate will form
How do you test for halide ions?
Add a couple of drops of dilute nitric acid and then silver nitrate solution then observe colour of preciptate
What colour precipitate do chloride ions produce?
White (silver chloride)
What colour precipitate do bromide ions produce?
Cream (silver bromide)
What colour precipitate do iodide ions produce?
Yellow (silver iodide)
What colour flame do lithium ions burn with?
Crimson
What colour flame do sodium ions burn with?
Yellow
What colour flame do potassium ions burn with?
Lilac
What colour flame do calcium ions burn with?
Orange-red
What colour flame do copper ions burn with?
Green
How do you test for metal ions using bunsen burners?
Clean platinum wire loop dipper in dilute hydrochloric acid and put it in flame till it burns without any colour
The dip it into sample and put back into flame
How do you test for metal hydroxides?
Add a few drops of sodium hydroxide and whatever colour precipitate can show you what metal is in the compound
What colour precipitate forms when calcium hydroxide is present?
White
What precipitate forms when copper (II) is present?
Blue
What colour precipitate forms when iron (II) hydroxide is present?
Green
What colour precipitate forms when iron (III) hydroxide is present?
Brown
What colour precipitate forms when aluminium hydroxide is present?
White at first but then redissolves
What colour precipitate forms when magnesium hydroxide is present?
White
What happens during flame emission spectroscopy?
Sample is placed in flame
Ions heat up and their electrons become excited
When the electrons drop back to their normal energy levels they transfer energy as light
Light passes through a spectroscope which detects different wave lengths of light to produce a line spectrum
What do the combinations of wavelengths emitted by an ion depend on?
Charge
Electron arrangement
What are the advantages of using machines?
Very sensitive (detect tiniest amounts of substances)
Very fast and tests can be automated
Very accurate
