C4 - Purifying and testing water Flashcards
1
Q
What is in water before it is purified?
A
- pollutants
- insoluble materials
- microbes
2
Q
What pollutants may get into tap water?
A
- pesticide residues
- nitrate residues
- lead compounds
3
Q
What are the three main stages of water purification?
A
Sedimentation: chemicals are added to make solid particles and bacteria settle out
Filtration: a layer of sand filters out the remaining fine particles
Chlorination: chlorine is added to kill microbes
4
Q
What is the test to see what is in water?
A
A precipitation reaction.
5
Q
What colour precipitate do chlorides give?
A
White precipitate.
6
Q
What colour precipitate do bromides give?
A
Cream precipitate.
7
Q
What colour precipitate do iodides give?
A
Yellow precipitate.
8
Q
What is barium chloride used to test for?
A
Sulfate ions.
9
Q
What is silver nitrate used to test for?
A
Halide ions.
