Acids and Alkalis
The PH Scale:
- Goes from 0 to 14
- 0 is strongly acidic, 14 is strongly alkaline and 7 is neutral
- Examples of acidic substances are... Vinegar, lemon juice and stomach acid.
- Examples of alkaline substances are... Washing up liquid, bleach and drain cleaner.
- Acids can become neutral by adding alkalis and vice versa.
The Neutralisation Equation:
- acid + alkali -> salt + water
- H+(aq) + OH-(aq) -> H2O(l)
- Universal indicator -> Red for an acid, purple for an alkali, green for neutral.
- Litmus paper -> Red for an acid, blue for an alkali, purple for neutral.
- Phenolphthalein -> Colourless for an acid, pink for an alkali.
- Methyl orange -> Red for an acid, yellow for an alkali.
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Reactions of Acids
Acids Reacting With Metal Oxides:
- acid + metal oxide -> salt + water
- Metal oxides are usually bases so they react with acids.
- E.g. hydrochloric acid + copper oxide -> copper chloride + water
- 2HCl + CuO -> CuCl3 + H2O
- E.g. sulphuric acid + zinc oxide -> zinc sulphate + water
- H2SO4 + ZnO -> ZnSO4 + H2O
Acids Reacting With Metal Carbonates:
- acid + metal carbonate -> salt + water + carbon dioxide
- E.g. hydrochloric acid + sodium carbonate -> sodium chloride + water + carbon dioxide
- 2HCl + Na2CO3 -> 2NaCl + H2O + CO2
- E.g. sulphuric acid + calcium carbonate -> calcium sulphate + water + carbon dioxide
- H2SO4 + CaCO3 -> CaSO4 + H2O + CO2
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