I can describe the characteristic properties of acids in terms of their reactions with (a) metals; (b) bases; (c) carbonates.
I can describe acids in terms of their effect on (a) litmus; (b); thymolphthalein; (c) methyl orange
I can describe the characteristic properties of bases in terms of their reactions with (a) acids; (b) ammonium salts.
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What do I know about acids and bases?
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What do I know about acids and bases?
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Properties of Acids
pH values of below 7
sour taste (when edible)
corrosive
can neutralise a base
form a salt and water
acids + water = forms hydrogen ions (H+)
presence of H+ ions = acidic solution
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HCl (aq) → H+ (aq) + Cl- (aq)
Example of acid
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Typical reactions of acids
Acids + metals
Only metals above hydrogen in the reactivity series will react with dilute acids.
Acid + Metal → Salt + Hydrogen
The name of the salt is related to the name of the acid used, as it depends on the anion within the acid
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Typical reactions of acids
Acids + metals
Only metals above hydrogen in the reactivity series will react with dilute acids.
Acid + Metal → Salt + Hydrogen
The name of the salt is related to the name of the acid used, as it depends on the anion within the acid
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Typical reactions of acids
Acids + bases
Metal oxides and metal hydroxides (alkalis) can act as bases
Acid + Base → Salt + Water (neutralisation)
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Typical reactions of acids
Acids + metal carbonates
Acid + Metal Carbonate → Salt + Carbon Dioxide + Water
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Indicators
Two colour indicators are used to distinguish between acids and alkalis
Many plants contain substances that can act as indicators and the most common one is litmuswhich is extracted from lichens
Synthetic indicators are organic compounds that are sensitive to changes in acidity and appear in different colours in acids and alkalis
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Synthetic Indicators
thymolphthalein
methyl orange
these two are frequently used in acid-alkali titrations
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Synthetic Indicators
used to show the endpoint in titrations as they have a very sharp
very sharp change of colour when an acid has been neutralised by alkali and vice-versa
Litmus is not suitable for titrations as the colour change is not sharp and it goes through a purple transition colour in neutral solutions making it difficult to determine an endpoint.
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Synthetic Indicators
Litmus is very useful as an indicator paper and comes in red and blue versions, for dipping into solutions or testing gases
