Question

Magnesium. aluminium, zinc and iron were put in different test tubes containing dilute
hydrochloric acid. In which test tube will the rate of formation of bubbles of hydrogen gas be
fastest and why?​

Answer 1

Reactions of metals with acids

Dilute acids react with relatively reactive metals such as magnesium, aluminium, zinc and iron. The products of the reaction are a salt plus hydrogen gas.

metal + acid → salt + hydrogen

Here’s a good way to remember it: MASH (M+A→S+H).

The name of the salt depends on the name of the acid. For example:

magnesium + hydrochloric acid → magnesium chloride + hydrogen

Mg + 2HCl → MgCl2 + H2

zinc + sulfuric acid → zinc sulfate + hydrogen

Zn + H2SO4 → ZnSO4 + H2

In general, the more reactive the metal, the faster the reaction. However, aluminium has a protective oxide layer, so it reacts slowly with acids to begin with.