Chemistry Unit 3: Hardness of water, the Haber process and functional groups

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How is hard water made?
Rain falls on rocks (e.g limestone or chalk) which dissolves the Mg2+ and Ca2+ ions into the water
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What are the advantages of hard water?
Ca2+ ions are good for the teeth and the minerals in the water make less risk of developing heart disease
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What is scum?
When the magnesium and calcium ions react with the soap they form scum which is insoluble
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What is scale?
It is a thermal insulator formed by hard water which builds up and reduces the efficiency of heating systems.
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What are two kinds of hardness?
Temporary: caused by the hydrocarbonate ion HCO3- in Ca(HCO3)2 and Permanent: caused by the dissolved calcium sulfate
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How can temporary hardness of water be removed?
When boiled the calcium hydrogencarbonate decomposes to form calcium carbonate which is the limestone on kettles
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How does adding sodium carbonate soften hard water?
The added carbonate ions react with Ca2+ and Mg2+ to make an insoluble precipitate of calcium and magnesium carbonate
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How does an ion exchange column soften hard water?
The ion exchange resin contains sodium ions which are replaced for calcium or magnesium ions in water.
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How can we use titration to compare the hardness of water?
The results would tell you: distilled water as no hardness, imported water is harder than local, local water contains temporary hardness and imported contains both temporary and permanent water.
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How is water from reservoirs treated?
It is passed through a mesh screen, chemicals are added to stick solids/microbes together, water is filtered, chlorination then removes remaining microbes and it is then distilled.
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Why are flouride and chlorine added?
Flouride reduces tooth decay however high doses of flouride can cause cancer or bone problems, Chlorine is added to prevent disease however it can increase the risk of certain cancers
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What is a closed system?
Where no products or reactants can enter or escape, if a reversible reaction occurs in a closed system then a state of equilibrium will be reached.
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How does temperature effect the equilibrium?
If you raise the temperature then the equilibrium would shift towards the endothermic reaction, if the temperature is lowered the equilibrium would shift towards the exothermic reaction.
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How does pressure effect the equilibrium?
if you raise the pressure then the equilibrium would shift towards the side of the least moles, if the pressure is decreased then the equilibrium would shift towards the side with most moles.
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What is the balanced equation of the Haber process? What are the required industrial conditions?
N2 + 3H2 2NH3 , Industrial conditions: 200 atmospheres of pressure, 450^C temp and iron catalyst
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What is the functional group of alcohols and what are some of their features?
Functional group of an alcohol is "-OH" and end in -ol e.g. methanol, they are flammable and dissolve in water, they are used as solvents and fuels.
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What is the functional group of carboxylic acids and what are some of their features?
Functional group of a carboxylic acid is "-COOH" e.g. ethanoic acid, they react with carbonates to form salt water &CO2, the salts they form end in -anoate, they dissolve in water and don't ionise completely so have higher pH than strong acids
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What are carboxylic acids used for?
Making soap and esters
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What is the functional group of esters and what are some of their features?
Functional group of esters is "-COO-" e.g. ethyl ethanoate, they smell nice,they are volatile, they are flammable, they dont mix well with water and aren't soluble, they mix well with alcohols and organic solvents, used in perfumes and flavourings
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How are esters formed?
ethanol + ethanoic acid -> ethyl ethanoate + water, the alcohol forms the "ethyl" part and the acid forms the "ethanoate" part
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What are the dangers of esters?
inhaling fumes irritates the mucous membranes in nose and mouth, they are highly flammable and are toxic
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Other cards in this set

Card 2

Front

What are the advantages of hard water?

Back

Ca2+ ions are good for the teeth and the minerals in the water make less risk of developing heart disease

Card 3

Front

What is scum?

Back

Preview of the front of card 3

Card 4

Front

What is scale?

Back

Preview of the front of card 4

Card 5

Front

What are two kinds of hardness?

Back

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