Characteristic Reactions of Acids
Metals and acids
- The typical reaction of a metal and an acid can be summarized as
acid + metal → salt + hydrogen
- For example:
2HCl (aq) + Zn (s) → ZnCl2 (aq) + H2 (g)
hydrochloric acid + zinc → zinc chloride + hydrogen
- Clearly, the extent of reaction depends on the reactivity of the metal and the strength of the acid
- Very reactive metals would react dangerously with acids and these reactions are not usually carried out
- Metals low in reactivity do not react at all, for instance copper does not react with dilute acids
- Stronger acids will react more vigorously with metals than weak acids. What signs of reaction would be expected to be different between the two?
- Faster reaction, seen as
- more effervescence
- the metal dissolves faster
- More exothermic
- Faster reaction, seen as
Metals and oxides
- The reaction of an acid with a metal oxide forms two products:
acid + metal oxide → salt + water
- For example:
2HCl (aq) + CaO (s) → CaCl2 (aq) + H2O (l)
hydrochloric acid + calcium oxide → calcium chloride + water
Metals and hydroxides
- The reaction with a metal hydroxide and an acid follows the same pattern as an oxide:
acid + metal hydroxide → salt + water
- A suitable example might be:
H2SO4 (aq) + Mg(OH)2 (s) → MgSO4 (aq) + 2H2O (l)
sulfuric acid + magnesium hydroxide → magnesium sulfate + water
Metals and carbonates
- The reaction between a metal carbonate and an acid produces three products:
acid + metal carbonate → salt + water + carbon dioxide
- For example:
2HNO3 (aq) + CuCO3 (s) → Cu(NO3)2 (aq) + H2O (l) + CO2 (g)
nitric acid + copper carbonate → copper nitrate + water + carbon dioxide
Metals and hydrogencarbonates
- The reaction between a metal hydrogencarbonate and an acid is the same as the carbonate reaction with a slight difference in stoichiometry:
acid + metal hydrogencarbonate → salt + water + carbon dioxide
- An example of this would be:
HCl (aq) + NaHCO3 (s) → NaCl (aq) + H2O (l) + CO2 (g)
hydrochloric acid + sodium hydrogencarbonate → sodium chloride + water + carbon dioxideExaminer Tip
Make sure you learn the formulae of the common acids and bases and that you can write examples of balanced equations of their characteristic reactions