3.2 Water Flashcards
What causes tempory hardness?
Dissolved calcium hydrogen carbonate which is Ca(HCO3)2
What are the two ions which affect hardness the most?
Calcium and Magnesium ions
What causes permanent hardness?
Dissolved calcium sulphate CaSO4
What substance softens hard water?
Sodium carbonate which is washing soda
What does filtration involve?
Putting the water through beds of sand and gravel. This removes large solids from the water
What does sedimentation involve?
Adding a chemical to remove very small solids from the water
What does chlorination involve ?
It involves chlorine gas being added to the water which kills bacteria
Name 3 common examples of how water can get polluted.
Fertilisers, pesticides, run off from nuclear power plants, lead from old pipes.
explain the causes and symptoms of fluorosis
Fluorosis is caused by taking in to much fluoride which can weaken bones and teeth
Explain the distribution of hard and soft water in the uk
The NW is softer the SE is harder (in general)
How much fluoride and for how long would it take for you to have skeletal fluorosis
10-20mg every day for 20 years
What is the chemical formula for water?
H20
What two chemicals are most renowned for causing a water sample to be hard?
Calcium (Ca) Magnesium (Mg)
What group on the periodic table causes hard water?
Group 2
What is the common name for the waste product produced when soap solution is added to a hard water sample?
Scum (calcium stearate)
“Drinking hard water can have health benefits” True or false?
True
What chemical is used in an ion exchange column to “soften” hard water?
Sodium (Na)
How can temporary hard water be purified?
By boiling the water sample
What cleaning detergent can be used with hard water without forming scum?
Soapless detergent
Which area of England typically has harder water?
The South-East
Which periodic group makes water harder when it’s ions are within the water?
Group 2
After running through limestone, which ions are dissolved in the water, making it harder?
Calcium ions
Which of the following is a group 2 element: Iron, Magnesium, Argon, Potassium, Water, Carbon dioxide, petrol, skin cell?And what effect would this have on water that it was dissolved in?
Magnesium - it would make the water harder.
What is a test for the hardness of water?
The hardness of a water sample can be tested by: adding soap solution to the water sample, shaking it, and adding more, and shaking more, until a permanent lather is former. Record the amount of soap solution needed for a permanent lather, and the more soap solution required, the harder the water.
What are the chemical names for scum? (Remember - there are two main metal ions that hard water is associated with)
Calcium stearate, or Magnesium stearate.
What is the equation for softening hard water?
Hard water (CaSO▼4(aq)) + Washing soda (Na▼2CO▼3(aq)) -> Scale (CaCO▼3(s)) + Softened water (Na▼2SO▼4(aq))
What is the piece of equipment used to soften harder water at the homes of people living in hard water areas?
An Ion Exchange
What is distilled water?
Water that has had it’s ions removed after being boiled in one container, then condensed in another.
What is deionised water?
Water with little to no metal ions dissolved in it. It is fundamentally different to distilled water, as it is not distilled, but instead an ion exchange column is used to remove the ions and exchange them for hydrogen, or Hydroxyl, neither of which would affect water hardness.
