Water Hardness and Treatment

The percentage of the earth's surface covered by water is
1. 70%
2. 7%
3. 20%
4. 2%
Study the diagram shown and select the process ocurring at A
1. Precipitation
2. Sublimation
3. Evaporation
4. Transpiration
Study the diagram shown and select the process ocurring at D
1. Evaporation
2. Sublimation
3. Precipitation
4. Transpiration
Study the diagram shown and select the process ocurring at C
1. Transpiration
2. Sublimation
3. Precipitation
4. Evaporation
Which one of the following is NOT a property of water?
1. It boils at 80 ºC
2. It has a density of 1 g/cm³
3. It is a good solvent
4. It clings to glass by capillary action
Water supplied to homes is treated by local councils in water treatment plants.
Which one of the following is NOT one of the stages of this water treatment?
1. Disinfection
2. Screening
3. Fluoridation
4. Settling
In a water treatment plant, water is treated before being sent to homes.
Which one of the following is the correct order of treatment in these plants?
1. Screening ➞ Settling ➞ Filtration ➞ Chlorination ➞ Fluoridation
2. Screening ➞ Filtration ➞ Settling ➞ Fluoridation ➞ Chlorination
3. Filtration ➞ Screening ➞ Settling ➞ Chlorination ➞ Fluoridation
4. Settling ➞ Screening ➞ Filtration ➞ Fluoridation ➞ Chlorination
One of the treatments of water for domestic use is to allow the water into large tanks where a flocculent such as aluminium sulfate helps small particles fall to the bottom.
This stage of the treatment is called
1. settling
2. fluoridation
3. screening
4. filtration
Which two of the following tests may be used for the detection of water?
1. Add the unknown liquid to anhydrous copper sulfate
2. Place blue cobalt chloride paper into the unknown liquid
3. Place a few drops of universal indicator into the unknown liquid
4. Throw a small piece of sodium into the unknown liquid
When water is treated at a water treatment plant, some chlorine is added to the water.
Why?
1. To kill any bacteria in the water
2. To remove solids from the water
3. Chlorine is good for our teeth
4. It causes solids in the water to settle to the bottom
In one of the stages of water treatment, a substance is added to the water in order that tooth decay may be reduced.
What is this stage called?
1. Fluoridation
2. Precipitation
3. Chlorination
4. Filtration
Rain is an example of
1. precipitation
2. perspiration
3. evaporation
4. respiration
If a beaker of water is left in a warm room for a few weeks, it is seen that the water 'disappears'.
What has happened to the water?
1. It has evaporated
2. It has precipitated
3. It has condensed
4. It has reacted with chemicals in the air to form a gas
If a beaker of water is left in a warm room for a few weeks, it will be observed that the water has changed into a vapour.
There wille also traces of a white solid on the inside of a beaker.
What conclusion can be drawn from this?
1. The water contained dissolved solids
2. There was salt (sodium chloride) in the water
3. Water is made up of molecules
4. There is hydrogen in the water
The diagram shows the electrolysis of water.
Why is some acid added to the water?
1. Water is a poor conductor of electricity
2. Water is a poor conductor of heat
3. The acid produces hydrogen and water vapour
4. The water is too alkaline
The diagram shows the electrolysis of water.
What are gases A and B?
1. A = hydrogen, B = oxygen
2. A = oxygen, B = hydrogen
3. A = hydrogen, B = water vapour
4. A = oxygen, B = methane
The diagram shows the electrolysis of water.
Which one of the following is a test for gas A?
1. It burns with a loud 'pop'
2. It re-ignites a glowing splint
3. It turns lime-water milky
4. It extinguishes a lighted candle
Flask A contains hard water.
Some of this water was poured into the tube containing ion-exchange resin.
The water that passed through the resin was collected in flask B.
Which one of the following would you use to compare the hardness of water samples in flasks A and B?
1. Soap solution
2. Universal indicator solution
3. Limewater
4. Copper sulfate solution
The diagram shows four test-tubes of water after 2 drops of soap solution had been added to each and shaken.
Which one of these test-tubes contained the hardest water sample?
1. Test tube D
2. Test tube A
3. Test tube B
4. Test tube C
Which two of the following metals, when in compound form are most likely to cause hardness in water?
1. Magnesium
2. Calcium
3. Sodium
4. Aluminium
Which one of the following is NOT a property of hard water?
1. It lathers easily with soap solution
2. It causes limescale in kettles
3. It has a nice taste
4. It is good for the brewing industry
Hard water in test tube A was heated and some water evaporated from it and condensed in test tube B.
Which one of the following statements is correct?
1. The water in test tube B is soft because only pure water evaporates in A and condenses in B
2. The water in B is soft because the cold water in the beaker cools the water in B and softens it
3. The water in A becomes soft as the hardness evaporates because of heating
4. The water in A becomes soft because hot water is softer than cold water
The diagram shows an apparatus used to decompose water by passing an electric current through it. The volumes of gas produced by this process are shown.
Which one of the following statements is correct?
1. Gas A is oxygen and it relights a glowing splint.
2. Gas A is oxygen and it burns with a pop.
3. Gas B is oxygen and it relights a glowing splint.
4. Gas B is hydrogen and it turns limewater milky.
Which one of the following compounds does NOT cause hardness in water?
1. Sodium chloride
2. Magnesium chloride
3. Calcium chloride
4. Magnesium sulfate
The diagram shows a Hofmann Voltammeter.
What are the parts labelled A and B?
1. A = platinum electrode, B = acidified water
2. A = platinum electrode, B = water
3. A = battery, B = sulfuric acid
4. A = battery, B = water
One of the methods of removing hardness from water is to use an ion-exchange resin, as used in water filter cartridges.
Which one of the following statements about ion-exchange resins is correct?
1. Calcium ions in the water are replaced by sodium ions from the resin.
2. Calcium ions in the water are replaced by chloride ions from the resin.
3. Magnesium ions in the water are replaced by calcium ions from the resin.
4. Chloride and magnesium ions in the water are replaced by calcium ions from the resin.
When water is being treated to make it safe for drinking, the first stage is to pass it through a wire mesh.
This stage is called
1. screening
2. chlorination
3. settling
4. filtration
At a water treatment plant, one of the stages involves passing water through a bed of sand and gravel.
This stage of treatment is called
1. filtration
2. screening
3. settling
4. fluoridation
Water behaves unusual at low temperatures.
Which one of the following statements about water's behaviour is incorrect?
1. A lake will freeze from the bottom up in freezing cold water.
2. Water is at its densest at 4ºC.
3. As water freezes below 0 ºC, it expands.
4. In a frozen lake, water gets warmer as the depth increases.
Two students investigated the hardness of different samples of water. They added drops of soap solution to 50 cm³ of each water sample and shook.
Their results are shown. Which sample of water is the softest?
1. Boiled tap water
2. River water
3. Spring water
4. Tap water
In the water cycle, what is the process by which water from the atmosphere gets back to the land and oceans?
1. Precipitation
2. Evaporation
3. Surface run-off
4. Condensation

Water Hardness and Treatment

Multiple Choice Quiz