Question
Explain with the chemical equation, what happens when water reacts with (a) alkali metals (Na, K), (b) heavier alkaline earth metals (Ca, Ba), (c) halogens.
Answer
(a) When water reacts with alkali metals such as sodium (Na) or potassium (K), the following reaction occurs:
2M + 2H2O → 2MOH + H2
where M represents the alkali metal. The alkali metal displaces hydrogen from water, resulting in the formation of metal hydroxide and the liberation of hydrogen gas.
(b) When water reacts with heavier alkaline earth metals such as calcium (Ca) or barium (Ba), the reaction is as follows:
Ca + 2H2O → Ca(OH)2 + H2
or
Ba + 2H2O → Ba(OH)2 + H2
In these reactions, the alkaline earth metal displaces hydrogen from water, leading to the formation of metal hydroxide and the release of hydrogen gas.
(c) When water reacts with halogens like chlorine (Cl2) or iodine (I2), the following reactions take place:
Cl2 + H2O → HCl + HClO
or
I2 + H2O → 2HI + HIO
In these reactions, the halogen reacts with water to produce corresponding acids and hypohalous acids.
