C4h: Purifying and Testing Water

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Give four different types of water resources in the UK.
Aquifers, Rivers, Reservoirs and Lakes.
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Why is water an important resource for many important industrial chemical processes?
It is used in solvent, cooler and cheap raw material.
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Give three pollutants that may be found in domestic water supplies.
Lead compounds, nitrate residues and pesticide residues.
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Name five types of substances present in water before it has been purified.
Insoluble materials, pollutants, microbes, dissolved minerals and dissolved salts.
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Which stage of purification kills microbes in water?
Chlorination.
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What solution is used to test sulfate ions?
Barium chloride solution
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What precipitate does sulfate ions give in a Barium Chloride solution?
A white precipitate.
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What solution is used to test halide ions?
Silver Nitrate solution.
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What precipitate does chloride ions give in a silver nitrate solution?
A white precipitate
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What precipitate does bromide ions give in a silver nitrate solution?
A cream precipitate
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What precipitate does iodide ions give in a silver nitrate solution?
A pale yellow precipitate
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What is the word equation for the precipitate reaction between barium chloride solution and sodium sulfate solution?
Barium chloride solution + sodium sulfate solution = sodium chloride solution + solid barium sulfate
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Why is it important to conserve water?
Because the amount of available fresh water is effectively limited. It also saves the materials and energy needed to treat and transport it.
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Why might drinking water contain nitrates?
Nitrate fertilisers are very soluble in water and are easily washed off fields by the rain and then into rivers and reservoirs. Because nitrates are all soluble they cannot easily be removed from the water.
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Why might drinking water contain lead compounds?
Older houses and water supply systems still rely on lead pipes. Poisonous lead compounds formed on the inside of the pipes slowly dissolve into the water.
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Why might drinking water contain pollutants?
Pesticides used by farmers to kill weeds or insects may be washed or blown into streams and rivers.
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What is the word equation for the precipitate reaction between silver nitrate solution and sodium bromide solution?
Silver nitrate solution + sodium bromide solution = sodium nitrate solution + solid silver bromide
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What is the word equation for the precipitate reaction between silver nitrate solution and sodium iodide solution?
Silver nitrate solution + sodium iodide solution = sodium nitrate solution + solid silver iodide
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What is the word equation for the precipitate reaction between silver nitrate solution and sodium chloride solution?
Silver nitrate solution + sodium chloride solution = sodium nitrate solution + solid silver chloride
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What are the three stages of purification?
Filtration, Sedimentation and Chlorination
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Describe the process of filtration.
The water is sprayed onto specially prepared layers of sand and gravel. As it trickles through, different sized insoluble solids are removed. The filter beds are cleaned periodically by pumping clean water backwards through the filter.
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Describe the process of sedimentation
A chemical is added which causes tiny solid particles (which would pass through a filter) to clump together into larger particles. These can then be allowed to settle out or may be filtered.
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Describe the process of chlorination
Chlorine gas, injected into the water, kills microbes.
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Why are some soluble substances not removed from water during purification? Give two examples.
Because they can't be filtered out. e.g. minerals which cause water hardness or some harmful or poisonous chemicals such as pesticides and fertilisers.
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What are the disadvantages of using distillation of sea water to make large quantities of fresh water?
It takes a lot of energy to boil water for this process,which would make the fresh water produced much more expensive than from traditional sources.There are problems disposing of the salt-rich waste water left over by the process.
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What state are barium chloride and silver nitrate?
(aq) aqueous
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What sort of reaction is the one to find sulfates or halides?
Precipitation reaction.
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What is the balanced symbol equation for the precipitate reaction between barium chloride solution and sodium sulfate solution?
BaCl˅2(aq) + Na˅2SO˅4(aq) = 2NaCl(aq) + BaSO˅4(s)
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What is the balanced symbol equation for the precipitate reaction between silver nitrate solution and sodium bromide solution?
AgNO˅3(aq) + NaBr(aq) → NaNO˅3(aq) + AgBr(s)
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What is the balanced symbol equation for the precipitate reaction between silver nitrate solution and sodium chloride solution?
AgNO˅3(aq) + NaCl(aq) → NaNO˅3(aq) + AgCl(s)
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What is the balanced symbol equation for the precipitate reaction between silver nitrate solution and sodium iodide solution?
AgNO˅3(aq) + NaI(aq) → NaNO˅3(aq) + AgI(s)
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Other cards in this set

Card 2

Front

Why is water an important resource for many important industrial chemical processes?

Back

It is used in solvent, cooler and cheap raw material.

Card 3

Front

Give three pollutants that may be found in domestic water supplies.

Back

Preview of the front of card 3

Card 4

Front

Name five types of substances present in water before it has been purified.

Back

Preview of the front of card 4

Card 5

Front

Which stage of purification kills microbes in water?

Back

Preview of the front of card 5
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