Solid sodium metal reacts with water, giving a solution of sodium hydroxide and releasing hydrogen gas. Write a balanced equation for the reaction using complete formulas for the compounds with phase labels.
Solution:
Let us first write down the chemical formulas.
Na_{(s)}+H_2O_{(l)}\rightarrow NaOH_{(aq)}+H_{2(g)}
Let us now balance this equation. Where you start to balance is up to you, generally, it is easier to balance elements that are alone. In this example, both Na and H are alone, so we can start with either.
The balanced equation is:
2Na_{(s)}+2H_2O_{(l)}\rightarrow 2NaOH_{(aq)}+H_{2(g)}
The reaction between sodium and water: