Acids Reacting with Metals
- Only metals above hydrogen in the reactivity series will react with dilute acids
- Therefore copper can not react with acids
- The more reactive the metal then the more vigorous the reaction will be
- Metals that are placed high on the reactivity series such as potassium and sodium are very dangerous and react explosively with acids
- When acids react with metals they form a salt and hydrogen gas:
- The general equation is:
metal + acid ⟶ salt + hydrogen
- Some examples of metal-acid reactions and their equations are given below:
Table of acid-metal reactions
| Metal | Sulfuric acid | Hydrochloric acid |
| Magnesium | Mg (s) + H2SO4 (aq) → MgSO4 (aq) + H2 (g) | Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g) |
| Zinc | Zn (s) + H2SO4 (aq) → ZnSO4 (aq) + H2 (g) | Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g) |
| Iron | Fe (s) + H2SO4 (aq) → FeSO4 (aq) + H2 (g) | Fe (s) + 2HCl (aq) → FeCl2 (aq) + H2 (g) |
- A salt is formed in this reaction
- In order to isolate the crystals of a salt (e.g. zinc sulfate) the following method should be used:
- React sulfuric acid with zinc metal
Zn (s) + H2SO4 (aq) → ZnSO4 (aq) + H2 (g)
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- Ensure the zinc metal is in excess to make sure all the acid is used up
- Wait for the reaction to finish, i.e. no more fizzing is observed
- Filter the solution into a beaker
- Boil the solution until crystals begin to form, this occurs when roughly half of the solution remains
- When cool, pour solution into an evaporating dish and then place in a warm oven for crystals to fully form
Examiner Tip
The general equation for the reaction of a metal with an acid can be remembered as MASH:
Metal + Acid → Salt + Hydrogen
The hydrogen gas produced will burn with a squeaky pop when ignited.
When making crystals from this reaction remember to say boil until crystals form as the method should not remove all of the water by heating directly in the beaker. This can decompose any crystals that have been formed.
