Question

A solution of a substance X is used for white washing. Name the substance X and write its formula. Write the reaction of the substance X named in above with water.

Answer 1

Reaction of quicklime with water:

• The substance which is used for white washing is Calcium oxide$\left(\mathrm{CaO}\right)$.
• Calcium oxide when reacted with water produces Calcium hydroxide(Lime water).
• This absorbs the Carbon dioxide present in the environment and produces Calcium carbonate.
• This Calcium carbonate forms a hard coating on the walls.
• The complete reaction is:

$$\begin{gathered} \underset{\mathrm{Calcium}\mathrm{oxide}}{\mathrm{CaO}\left(\mathrm{s}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\mathrm{Calcium}\mathrm{hydroxide}}{\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)} \\ \underset{\mathrm{Calcium}\mathrm{hydroxide}}{\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Caclium}\mathrm{carbonate}}{{\mathrm{CaCO}}_3\left(\mathrm{s}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)} \end{gathered}$$

Therefore, the substance X is Calcium oxide$\left(\mathrm{CaO}\right)$.