The table summarises some reactions of metals in the reactivity series. Hydrogen and carbon are shown for comparison.
When a metal reacts with water, a metal hydroxide and hydrogen are formed. For example, sodium reacts rapidly with cold water:
Sodium + water → sodium hydroxide + hydrogen
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
In general, the more reactive the metal, the more rapid the reaction is.
Describe and explain the observations when a small piece of lithium is placed on the surface of a big container of water. A few drops of universal indicator have been added to the water.
There is fizzing as the lithium reacts with the water to produce hydrogen gas. The colour of the universal indicator changes from green to purple as an alkaline solution of lithium hydroxide is produced.
Magnesium + hydrochloric acid → magnesium chloride + hydrogen
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
The more reactive the metal, the more rapid the reaction is. A metal below hydrogen in the reactivity series will not react with dilute acids.
Platinum is placed below gold in the reactivity series. Predict its reaction with dilute acids and explain your answer.
Platinum will not react with dilute acids. Metals below hydrogen in the reactivity series do not react with dilute acids, and both gold and platinum are placed below hydrogen.