C2 7.1 (a) Acids

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C2 7.1 (a) Acids
L/O Acids produce H ions
Alkalis produce OH- ions The pH
scale measures the H ion
concentration
Acids in everyday life
Name of acid
Where it is found
Formula
citric
Lemons , oranges
C6H7O7 H
sulphuric
Car battery
H2 SO4
methanoic
wasp ant stings
CHOO H
hydrochloric
In the stomach
H CL
tannic
tea
C34H28O21
lactic
Sour milk
CH3CH(OH)COO H
ethanoic
vinegar
C2H3OO H
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Acids in food and drink
Sauces and pickles contain ethanoic acid -
vinegar Vinegar preserves fruits and vegetables
Fizzy drinks are made by adding carbon dioxide
gas under pressure forming carbonic acid
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Aqueous solution this occurs when a substance
dissolves in water
Dissolving Hydrogen chloride gas in water
HCl (g)
H (aq) Cl - (aq)
All acids form H ions when added to
water. It is the hydrogen ions that make a
solution acidic.
Other properties of acids turn blue litmus
red conduct electricity ( electrolytes)
have a sour taste have a pH less than 7
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C2 7.1 (b) Bases and alkalis
CuO MgO ZnO
Other properties of alkalis turn red
litmus blue conduct electricity soapy to
touch have pH more than 7
Bases are usually metal oxides or hydroxides and
can neutralise acids. Eg CuO
NaOH NH4OH KOH
NaOH NH4OH KOH
An alkali is a soluble base. Eg NaOH
It is the OH- ion ( hydroxide ion ) which
make a solution alkaline
NaOH (s) Na (aq)
OH - (aq) Sodium hydroxide solution is
formed when sodium hydroxide crystals are
dissolved in water
water
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C2 7.1 (c) Measuring acidity
Indicators are chemicals which change colour
when added to acids or alkalis.
Eg. Unversal indicator - a mixture of different
chemicals which change colour at different
acidity strengths
pH scale means power of hydrogen ions present
0-most acidic 14-most alkaline
An H ion is a hydrogen atom which has lost its
electron. so an acid is a proton donor
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C2 7.2 (a) Acids and metals
L/O acid metal salt hydrogen
acid base salt water
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zinc
hydrogen
sulphate
hydrogen
sodium
chloride
hydrogen
potassium
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C2 7.2 (b) Acids and insoluble bases
Neutralisation reaction
H (aq) OH- (aq) H2O (l)
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C2 7.2 (b) Acids and insoluble bases
Neutralisation reaction
H (aq) OH- (aq) H2O (l)
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Zinc Sulfate
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neutralisation
salt
water
hydrogen
metals
bases
Wasp stings are alkali enzymes
Dock leaves are alkali and can neutralise
nettle stings (methanoic acid)
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