f Flashcards
What is a pure substance
A substance, either element or compound, that is not mixed with any other substance
Pure substances have…
Specific melting and boiling points
What does paper chromatography do?
It allows us to separate substances based on their different solubilities
Chromatography paper set up
Draw line in pencil on the paper (stationary phase)- dot of colour goes on the line. Put the paper in a solvent (mobile phase) under the line (not submerging the dots.
What will pure compounds form in paper chromatography
One single spot
What will compounds in a mixture form in paper chromatography
Multiple spots
Why do you draw the line in pencil?
So that the ink doesn’t also move up the page
How to find Rf Values paper chromatography?
distance moved by substance/distance moved by solvent
How to test for hydrogen
We insert a burning splint when the hydrogen gas burns and produces a pop sound
How to test for oxygen
Glowing splint will relight
How to test for carbon dioxide
Bubble through limewater (aqueous calcium hydroxide) and turns cloudy
How to test for chlorine
Insert damp litmus paper into the test tube, and bleaches it
What flame does lithium ion produce
Crimson
What flame does sodium ion produce
Yellow
What flame does potassium ion produce
Lilac
What flame does calcium ion produce
Orange-red
What flame does copper ion produce
Green
What colour precipitate do calcium, magnesium and aluminium form when combined with sodium hydroxide
White
How do you work out which white precipitate is aluminium?
Add an excess of NaOH
What colour do copper 2+ ions turn when reacted with sodium hydroxide
Blue- copper (II) hydroxide
What colour do Iron 2+ ions turn when reacted with sodium hydroxide
Green- iron (II) hydroxide
What colour do Iron 3+ ions turn when reacted with sodium hydroxide
Brown-red- Iron (III) hydroxide
How to test for a carbonate ion
Add dilute acid to the sample
The acid will react with the carbonate to make CO2 gas
Bubble the gas through limewater to make sure that we have carbon dioxide and therefore started with a carbonate ion
How to test for halide ions
Add dilute nitric acid
Then add dilute silver nitrate solution
Halides each produce a precipitate of the silver halide
What colour 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
How to test for sulfate ions
Add dilute HCL to our sample
Add barium chloride solution
If sulfate ions are present, we will see a white precipitate
What is the solvent front in chromatography
The top of the solvent
What is potable water
Water that’s safe to drink
Criteria for potable water
Level of dissolved substances need to be fairly low
pH between 6.5-8.5
No microorganisms in it
How to make water potable
Fresh water passed through wire mesh to remove big things
Bed of sand and gravel to filter out smaller bits
Sterilise by bubbling chlorine gas through/using ozone or UV light
How to desalinate water
Use distillation to get pure distilled water
Reverse osmosis- pass salty water through a membrane that only lets water molecules through
Sources of wastewater
Domestic
Agricultural systems
Industrial
How to treat sewage
Run through mesh to remove large objects
‘Sedimentation’ allows for sludge to sink to the bottom and the lighter effluent to stay at the top
Breakdown organic matter biologically by microorganisms
