Acids Reacting with Metals (WJEC GCSE Chemistry)
Revision Note
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)
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 Tips and Tricks
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.
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