Hard Water Flashcards
What is the difference between hard and soft water, with soap?
Hard water produces a scum, so you need more soap.
What does hard water produce when heated?
Furring or scale.
What does scale do to heating systems?
Reduces efficiency and can block pipes.
What is permanent hardness caused by?
Dissolved calcium sulfate.
Why is water hard?
Rain falls on rocks (limestone, chalk, gypsum etc.) and can dissolve compounds like magnesium sulfate or calcium sulfate
What are the benefits of hard water?
- Ca2+ ions are good for teeth and bones
2. Less risk of heart disease
What is temporary hardness caused by?
Hydrogencarbonate ion, HCO3-.
How can temporary hardness be removed?
Boiling.
Why does boiling remove temporary hardness?
The calcium hydrogencarbonate decomposes to form calcium carbonate.
Why does adding washing soda remove hardness?
The carbonate ions react with the Ca2+ and Mg2+ ions to make an insoluble precipitate.
How do ion exchange columns work?
The sodium ions are exchanged for calcium or magnesium ions in the water.
How can you compare the hardness of water samples?
Titration.
What diseases can microbes in water cause?
Cholera and dysentry.
What are the stages of water treatment?
- Mesh (e.g twigs)
- Chemicals (e.g microbes)
- Gravel bed (e.g solids)
- Chlorination (e.g microbes)
What does carbon do in filters?
Removes chlorine taste.
What does silver do in filters?
Kill bugs.
How is pure water produced?
Distillation.
Why isn’t tap water distilled?
Too expensive.
Why is fluoride added to drinking water?
Reduces tooth decay.
Why is chlorine added to drinking water?
Prevent disease.
What is the problem with adding fluoride to drinking water?
- Can cause cancer and bone problems.
2. People can’t choose not to use tap-water (mass-medication).
What is the problem with adding chlorine to drinking water?
Can react with natural substances in water to produce toxic by-products.
