Purifying and Testing Water Flashcards
Where is the largest source of water
Reservoirs
Water is important for industry
How is it used
For cooling
As a solvent
A cheap raw material
In Britain why is it important not to waste water
Demand for water is higher than supply in some parts
What can untreated (raw) water contain
Insoluble particles
Pollutants
Microbes
Dissolved salts and minerals
Typical water treatment process:
Sedimentation- water settles to allow insoluble particles to sink
Filtration- removes fine particles
Cholrination- kills microorganisms in water
Is tap water pure
What will it contain
No it is not pure
It contains soluble materials not removed by the normal water treatment process. It is possible some are poisonous so extra steps are taken.
Water must be distilled to make sure it is pure
What are the problems with distilling water
Uses lots of energy and is costly
Why can’t we distil sea water
Huge amounts of energy would be needed
It is corrosive so equipment would be costly
What pollutants could we find in water supplies
They are more difficult to remove
Nitrates from fertiliser run-off
Lead compounds from old lead pipes
Pesticides from nearby crops
What do dissolved ions of salts undergo to be identified
How will this occur
Precipitation reaction. This is done when two solutions are mixed and an insoluble solid is formed
How can sulphates be detected in water
By using barium chloride solution
a white precipitate of barium sulphate will form
Silver nitrate solution detects what in water
What makes them?
Halide ions
Halides are the ions made by halogens
With silver nitrate, if a chloride is detected what will it form
A white precipitate
With silver nitrate, if a bromide is detected what will it form
A cream precipitate
With silver nitrate, if an iodide is detected what will it form
A yellow precipitate
