C3- water Flashcards
Why is rainwater naturally slightly acidic?
because it contains carbonic acid, formed by the reaction between water and carbon dioxide in the atmosphere.
What is Hard Water?
Is water that contains dissolved compounds, usually calcium or magnesium compounds.
How does the carbonic acid in rainwater react with hard water?
Carbonic acid in rainwater reacts with this to produce soluble calcium hydrogencarbonate:
carbonic acid + calcium carbonate → calcium hydrogencarbonate
H2CO3(aq) + CaCO3(s) → Ca(HCO3)2(aq)
What does soft water form with soap?
Lather.
What does hard water form with soap?
The dissolved calcium ions and magnesium ions in hard water react with the soap to form scum, so more soap is needed.
What determines whether water is soft or hard?
The types of rocks found in different regions determines how hard or soft the water will be. The water in some parts of the country is soft because it has low levels of dissolved calcium and magnesium compounds, while the water in other parts of the country is hard because it has higher levels of dissolved calcium and magnesium compounds.
How do you perform a titration with a soap solution to find out that hardness of water?
A known volume of water is put into a conical flask. Soap solution is added to it from a burette or pipette. The mixture is swirled to help it form lather. The volume of soap solution that needs to be added to form permanent lather is recorded. The harder the water, the greater the volume of soap solution needed.
What is the difference between temporary hard water, and permanent hard water?
Temporary hard water can be softened by boiling it. Permanent hard water stays hard, even when it is boiled.
Why does temporary hard water get softened when boiled?
Temporary hard water contains dissolved hydrogen carbonate ions, HCO 3–. When heated, these ions decompose (break down) to form carbonate ions, CO3 2–. The carbonate ions in the boiled water react with dissolved calcium and magnesium ions to form insoluble precipitates (calcium carbonate and magnesium carbonate).
Why does permanent hard water not get softened when boiled?
Permanent hard water contains dissolved sulfate ions, SO4 2–. These do not decompose when heated. They remain dissolved and do not react with calcium and magnesium ions - so the water stays hard even when boiled.
What are the advantages of hard water?
can improve the taste of the water
are good for the development and maintenance of bones and teeth can help to reduce heart disease
What are the disadvantages of hard water?
More soap is needed to produce lather, which increases costs. This happens with temporary or permanent hardness.
The scum produced is unsightly - spoiling the appearance of baths and shower screens, for example.
Temporary hardness can reduce the efficiency of kettles and heating systems
Why does temporary hard water reduce the efficiency of heating systems?
This is because limescale (a solid containing calcium carbonate) is produced when the water is heated. It coats the heating element in kettles, and the inside of boilers and hot water pipes. This means more energy is needed to heat the water, again increasing costs. Pipes may become blocked by limescale - causing the heating system to break down.
How can you soften hard water?
Methods for softening hard water involve the removal of calcium ions and magnesium ions from the water.
There are two methods for softening hard water:
adding sodium carbonate to the water
using ion exchange columns
How can you soften hard water?
Methods for softening hard water involve the removal of calcium ions and magnesium ions from the water.
There are two methods for softening hard water:
adding sodium carbonate to the water
using ion exchange columns
What is the chemical formula of sodium carbonate and what is it also known as?
Sodium carbonate, Na2CO3, is also known as washing soda.
What is the chemical formula of sodium carbonate and what is it also known as?
Sodium carbonate, Na2CO3, is also known as washing soda.
How does adding sodium carbonate to hard water soften it? (use an equation)
Sodium carbonate is soluble but calcium carbonate and magnesium carbonate are insoluble.
The carbonate ions from sodium carbonate react with the calcium and magnesium ions in the water to produce insoluble precipitates. For example:
calcium ions + sodium carbonate → calcium carbonate + sodium ions
Ca2+(aq) + Na2CO3(aq) → CaCO3(s) + 2Na+(aq)
The water is softened because it no longer contains dissolved calcium ions and magnesium ions. It will form lather more easily with soap.
How does adding sodium carbonate to hard water soften it? (use an equation)
Sodium carbonate is soluble but calcium carbonate and magnesium carbonate are insoluble.
The carbonate ions from sodium carbonate react with the calcium and magnesium ions in the water to produce insoluble precipitates. For example:
calcium ions + sodium carbonate → calcium carbonate + sodium ions
Ca2+(aq) + Na2CO3(aq) → CaCO3(s) + 2Na+(aq)
The water is softened because it no longer contains dissolved calcium ions and magnesium ions. It will form lather more easily with soap.
What are the disadvantages of using sodium carbonate to soften hard water?
the calcium carbonate and magnesium carbonate precipitates to form limescale. As well as being unsightly on your taps, it can also clog up pipes in heating systems (causing them to break down). This makes treatment with sodium carbonate suitable for softening water only in certain circumstances - such as softening water for hand washing clothes.
What are the disadvantages of using sodium carbonate to soften hard water?
the calcium carbonate and magnesium carbonate precipitates to form limescale. As well as being unsightly on your taps, it can also clog up pipes in heating systems (causing them to break down). This makes treatment with sodium carbonate suitable for softening water only in certain circumstances - such as softening water for hand washing clothes.
What are ion exchange columns?
Commercial water softeners often use ion exchange resins. These substances are usually made into beads, which are packed into cylinders called ion exchange columns. These can be built into machines, such as dishwashers, or plumbed into water systems to continuously soften the water.
What are ion exchange columns?
Commercial water softeners often use ion exchange resins. These substances are usually made into beads, which are packed into cylinders called ion exchange columns. These can be built into machines, such as dishwashers, or plumbed into water systems to continuously soften the water.
How do ion exchange columns work?
The resin beads have sodium ions attached to them. As the hard water passes through the column, the calcium and magnesium ions swap places with the sodium ions.
The calcium and magnesium ions are left attached to the beads, while the water leaving the column contains more sodium ions. The hard water is softened because it no longer contains calcium or magnesium ions. Some ion exchange resins use hydrogen ions instead of sodium ions.
How do ion exchange columns work?
The resin beads have sodium ions attached to them. As the hard water passes through the column, the calcium and magnesium ions swap places with the sodium ions.
The calcium and magnesium ions are left attached to the beads, while the water leaving the column contains more sodium ions. The hard water is softened because it no longer contains calcium or magnesium ions. Some ion exchange resins use hydrogen ions instead of sodium ions.
What must have to resin beads after softening hard water?
Once the resin beads in dishwashers become saturated with calcium and magnesium ions, they must be regenerated by adding sodium chloride (common salt). The sodium ions it contains replace the calcium and magnesium ions on the beads.
What must have to resin beads after softening hard water?
Once the resin beads in dishwashers become saturated with calcium and magnesium ions, they must be regenerated by adding sodium chloride (common salt). The sodium ions it contains replace the calcium and magnesium ions on the beads.
What are the advantages of using ion exchange columns?
Sodium chloride is cheap and widely available, making this a convenient and cost-effective system.
What are the advantages of using ion exchange columns?
Sodium chloride is cheap and widely available, making this a convenient and cost-effective system.
What must we do to produce water of suffucient quality?
choose an appropriate source of water
filter the water
chlorinate the water
What must we do to produce water of suffucient quality?
choose an appropriate source of water
filter the water
chlorinate the water
What are the sources of water typically used in the UK?
lakes, rivers, aquifers and reservoirs.
What are the sources of water typically used in the UK?
lakes, rivers, aquifers and reservoirs.
What is an aquifer?
An aquifer is an underground layer of permeable rock, gravel or sand that is soaked with water
What is an aquifer?
An aquifer is an underground layer of permeable rock, gravel or sand that is soaked with water
What is a resourvoir?
a reservoir is usually an artificial lake, made by building a dam to accumulate and save river water in the valley behind.
What is a resourvoir?
a reservoir is usually an artificial lake, made by building a dam to accumulate and save river water in the valley behind.
What are boreholes?
In countries where water is scarce, boreholes are drilled to reach water underground.
What are boreholes?
In countries where water is scarce, boreholes are drilled to reach water underground.
How do you first filter the water?
Solids in the water, such as leaves and soil, must be removed with the screen. The water is sprayed onto specially-prepared layers of sand and gravel called filter beds.
Different-sized insoluble solids are removed as the water trickles through the filter beds. These are cleaned every so often by pumping clean water backwards through the filter.
How do you first filter the water?
Solids in the water, such as leaves and soil, must be removed with the screen. The water is sprayed onto specially-prepared layers of sand and gravel called filter beds.
Different-sized insoluble solids are removed as the water trickles through the filter beds. These are cleaned every so often by pumping clean water backwards through the filter.
What happens to the water next? (sedimentation tank)
The water is then passed into a sedimentation tank. Aluminium sulfate is added to clump tiny particles together to make larger particles, which settle out more easily. The water is then passed through a fine filter, such as carbon granules, to remove very small particles.
What happens to the water next? (sedimentation tank)
The water is then passed into a sedimentation tank. Aluminium sulfate is added to clump tiny particles together to make larger particles, which settle out more easily. The water is then passed through a fine filter, such as carbon granules, to remove very small particles.
What happens to the water after the sedimentation tank and why?
Chlorine is added to drinking water to sterilise it. The chlorine kills microbes - including microbes that cause potentially-fatal diseases such as typhoid, cholera and dysentery.
What happens to the water after the sedimentation tank and why?
Chlorine is added to drinking water to sterilise it. The chlorine kills microbes - including microbes that cause potentially-fatal diseases such as typhoid, cholera and dysentery.
What is the order by which water is purified?
Screen, coarse filter, sedimentation tank, Fine filter, chrlorine added, then into a storage tanks, and then into homes and factories.
What is the order by which water is purified?
Screen, coarse filter, sedimentation tank, Fine filter, chrlorine added, then into a storage tanks, and then into homes and factories.
What are the advantages of fluoridated water?
Results from scientific research indicate that fluoridated water can improve dental health by reducing tooth decay. Many areas of the country naturally have low fluoride levels present in the water supply.
What are the advantages of fluoridated water?
Results from scientific research indicate that fluoridated water can improve dental health by reducing tooth decay. Many areas of the country naturally have low fluoride levels present in the water supply.
What are the arguements agaisnt fluorine being added to water?
has been linked to tooth mottling (staining), bone disease and pain
forces people to consume fluoride when they drink tap water - taking away their personal choice (making it unethical)
What are the arguements agaisnt fluorine being added to water?
has been linked to tooth mottling (staining), bone disease and pain
forces people to consume fluoride when they drink tap water - taking away their personal choice (making it unethical)
Why is water from the tap not pure?
because it contains dissolved mineral ions and chlorine.
Why is water from the tap not pure?
because it contains dissolved mineral ions and chlorine.
What are the advantages of filtering water at home?
Filtering removes impurities and this can improve the taste and quality of the water. Filtering also helps to soften the water.
What are the advantages of filtering water at home?
Filtering removes impurities and this can improve the taste and quality of the water. Filtering also helps to soften the water.
What do water filter cartridges contain?
silver to kill bacteria
carbon (‘activated charcoal’) to absorb impurities, eg chlorine
ion exchange resins to soften the water, and remove heavy metal ions (such as lead ions)
What do water filter cartridges contain?
silver to kill bacteria
carbon (‘activated charcoal’) to absorb impurities, eg chlorine
ion exchange resins to soften the water, and remove heavy metal ions (such as lead ions)
Why is silver used in filter cartridges?
Silver nanoparticles have an antibacterial effect. Their presence in the filter prevents the growth of bacteria within the filter if water is left inside it for long periods. Silver nanoparticles also help break down harmful pesticides which might be in the water.
Why is silver used in filter cartridges?
Silver nanoparticles have an antibacterial effect. Their presence in the filter prevents the growth of bacteria within the filter if water is left inside it for long periods. Silver nanoparticles also help break down harmful pesticides which might be in the water.
How can you get pure water from seawater?
pure water can be produced from seawater by distillation.
During distillation, the seawater is boiled. The water vapour is then cooled and condensed to form pure water - leaving the salt behind.
How can you get pure water from seawater?
pure water can be produced from seawater by distillation.
During distillation, the seawater is boiled. The water vapour is then cooled and condensed to form pure water - leaving the salt behind.
What is the disadvantage of distilling seawater in order to produce pure water?
it is expensive because large amounts of energy are needed to heat the seawater
it increases the use of fossil fuels - which are non-renewable resources
carbon dioxide emissions from burning fossil fuels contribute to global warming
What is the disadvantage of distilling seawater in order to produce pure water?
it is expensive because large amounts of energy are needed to heat the seawater
it increases the use of fossil fuels - which are non-renewable resources
carbon dioxide emissions from burning fossil fuels contribute to global warming
How can you test if water is pure?
measuring its boiling point
evaporating it (to dryness) on an evaporating dish
How can you test if water is pure?
measuring its boiling point
evaporating it (to dryness) on an evaporating dish
What happens to pure water and its boiling point?
Pure water boils at 100°C, but its boiling point increases as the concentration of dissolved salts increases.
What happens to pure water and its boiling point?
Pure water boils at 100°C, but its boiling point increases as the concentration of dissolved salts increases.
What happens when you evaporate pure water?
Pure water will leave no solids behind when it is evaporated, whereas impure water will leave solids behind on the evaporating dish.
What happens when you evaporate pure water?
Pure water will leave no solids behind when it is evaporated, whereas impure water will leave solids behind on the evaporating dish.
