Acids and Alkalis and Reactions of Acids

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)

Indicators:

• 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.

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