When a metalShiny element that is a good conductor of electricity and heat, and which forms basic oxides. reacts with water, a metal hydroxide and hydrogen are formed.
Group 1
Sodium reacts rapidly with cold water. The word equation is:
sodium + water → sodium hydroxide + hydrogen
The balanced chemical equation is:
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
Group 2
The formulaA combination of symbols that indicates the chemical composition of a substance. of a group 1 metal hydroxide is different to a group 2 metal hydroxide. This affects the balanced chemical equationA chemical equation written using the symbols and formulae of the reactants and products, so that the number of units of each element present is the same on both sides of the arrow. of the chemical equations.
Calcium reacts more slowly with cold water. The word equation is:
calcium + water → calcium hydroxide + hydrogen
The balanced chemical equation is:
Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)
Reaction of metals with dilute acids
When a metal reacts with a dilute acidSubstance producing more hydrogen ions than hydroxide ions when dissolved in water. , a saltThe substance formed when the hydrogen ion in an acid is replaced by a metal ion. and hydrogen are formed.
The more reactiveThe tendency of a substance to undergo a chemical reaction. the metal, the more rapid the reaction is. A metal below hydrogen in the reactivity seriesA list of elements in order of their reactivity, usually from most reactive to least reactive. will not react with dilute acids.
For example, magnesium reacts rapidly with dilute hydrochloric acid: