contains dissolved compounds, usually of calcium or magnesium. The compounds are dissolved when water comes into contact with rocks.
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Temporary hard water
contains hydrogencarbonate ions (HCO3 ––) that decompose on heating to produce carbonate ions which react with calcium and magnesium ions to form precipitates.
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Benfits of hard water
calcium compounds are good for the development and maintenance of bones and teeth and also help to reduce heart disease.
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exothermic reaction
energy released from forming new bonds is greater than the energy needed to break existing bonds
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endothermic reaction
energy needed to break existing bonds is greater than the energy released from forming new bonds
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Haber process
The raw materials for the Haber process are nitrogen and hydrogen. Nitrogen is obtained from the air and hydrogen may be obtained from natural gas or other sources.
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reversible reaction
When a reversible reaction occurs in a closed system, equilibrium is reached when the reactions occur at exactly the same rate in each direction.
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gaseous reactions
an increase in pressure will favour the reaction that produces the least number of molecules as shown by the symbol equation for that reaction.
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Alcohols
contain the functional group –OH. Methanol, ethanol and propanol are the first three members of a homologous series of alcohols
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Methanol, ethanol and propanol
■ dissolve in water to form a neutral solution ■ react with sodium to produce hydrogen ■ burn in air ■ are used as fuels and solvents, and ethanol is the main alcohol in alcoholic drinks.
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Ethanoic acid
d is a member of the carboxylic acids, which have the functional group –COOH.
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Carboxylic acids
■ dissolve in water to produce acidic solutions ■ react with carbonates to produce carbon dioxide ■ react with alcohols in the presence of an acid catalyst to produce esters ■ do not ionise completely when dissolved in water and so are weak acids
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aqueous solutions
of weak acids have a higher pH value than aqueous solutions of strong acids with the same concentration.
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Esters
Ethyl ethanoate is the ester produced from ethanol and ethanoic acid. Esters have the functional group –COO–. They are volatile compounds with distinctive smells and are used as flavourings and perfumes.
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Other cards in this set
Card 2
Front
Temporary hard water
Back
contains hydrogencarbonate ions (HCO3 ––) that decompose on heating to produce carbonate ions which react with calcium and magnesium ions to form precipitates.
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