Question

Write the balanced equation to describe the reaction between Sodium metal and cold water. What would be observed when four drops of Phenolphthalein are added to the reaction mixture.

Answer 1

Formation of the base Sodium hydroxide (NaOH)

The balanced equation of the reaction between Sodium metal and cold water is:

$$\begin{gathered} 2\mathrm{Na}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right) \\ \mathrm{Sodium}\mathrm{water}\mathrm{sodium}\mathrm{hydrogen} \\ \mathrm{metal}\mathrm{hydroxide}\mathrm{gas} \end{gathered}$$

Phenolphthalein is a chemical indicator. This indicator has a tendency to give pink colour to the basic solution. It turns colourless when treated with an acidic solution.

The reaction mixture is basic in nature. Hence, when four drops of phenolphthalein are added to the reaction mixture then we will observe a pink colour.