3.2 Water

Question 0

What causes tempory hardness?

Answer 0

Dissolved calcium hydrogen carbonate which is Ca(HCO3)2

Question 1

What are the two ions which affect hardness the most?

Answer 1

Calcium and Magnesium ions

Question 2

What causes permanent hardness?

Answer 2

Dissolved calcium sulphate CaSO4

Question 3

What substance softens hard water?

Answer 3

Sodium carbonate which is washing soda

Question 4

What does filtration involve?

Answer 4

Putting the water through beds of sand and gravel. This removes large solids from the water

Question 5

What does sedimentation involve?

Answer 5

Adding a chemical to remove very small solids from the water

Question 6

What does chlorination involve ?

Answer 6

It involves chlorine gas being added to the water which kills bacteria

Question 7

Name 3 common examples of how water can get polluted.

Answer 7

Fertilisers, pesticides, run off from nuclear power plants, lead from old pipes.

Question 8

explain the causes and symptoms of fluorosis

Answer 8

Fluorosis is caused by taking in to much fluoride which can weaken bones and teeth

Question 9

Explain the distribution of hard and soft water in the uk

Answer 9

The NW is softer the SE is harder (in general)

Question 10

How much fluoride and for how long would it take for you to have skeletal fluorosis

Answer 10

10-20mg every day for 20 years

Question 11

What is the chemical formula for water?

Answer 11

H20

Question 12

What two chemicals are most renowned for causing a water sample to be hard?

Answer 12

Calcium (Ca) Magnesium (Mg)

Question 13

What group on the periodic table causes hard water?

Answer 13

Group 2

Question 14

What is the common name for the waste product produced when soap solution is added to a hard water sample?

Answer 14

Scum (calcium stearate)

Question 15

“Drinking hard water can have health benefits” True or false?

Answer 15

True

Question 16

What chemical is used in an ion exchange column to “soften” hard water?

Answer 16

Sodium (Na)

Question 17

How can temporary hard water be purified?

Answer 17

By boiling the water sample

Question 18

What cleaning detergent can be used with hard water without forming scum?

Answer 18

Soapless detergent

Question 19

Which area of England typically has harder water?

Answer 19

The South-East

Question 20

Which periodic group makes water harder when it’s ions are within the water?

Answer 20

Group 2

Question 21

After running through limestone, which ions are dissolved in the water, making it harder?

Answer 21

Calcium ions

Question 22

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?

Answer 22

Magnesium - it would make the water harder.

Question 23

What is a test for the hardness of water?

Answer 23

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.

Question 24

What are the chemical names for scum? (Remember - there are two main metal ions that hard water is associated with)

Answer 24

Calcium stearate, or Magnesium stearate.

Question 25

What is the equation for softening hard water?

Answer 25

Hard water (CaSO▼4(aq)) + Washing soda (Na▼2CO▼3(aq)) -> Scale (CaCO▼3(s)) + Softened water (Na▼2SO▼4(aq))

Question 26

What is the piece of equipment used to soften harder water at the homes of people living in hard water areas?

Answer 26

An Ion Exchange

Question 27

What is distilled water?

Answer 27

Water that has had it’s ions removed after being boiled in one container, then condensed in another.

Question 28

What is deionised water?

Answer 28

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.