Question

What happen to the crystals of washing soda when exposed to air? Name the phenomenon exhibited.

Answer 1

When exposed to air, sodium carbonate decahydrate (${\mathrm{Na}}_2{\mathrm{CO}}_3.10{\mathrm{H}}_2\mathrm{O}$) or washing soda crystal slowly loses its water of crystallisation and gets converted into white powder.

$$\begin{gathered} {\mathrm{Na}}_2{\mathrm{CO}}_3.10{\mathrm{H}}_2\mathrm{O}\stackrel{\mathrm{Air}}{\to }{\mathrm{Na}}_2{\mathrm{CO}}_3.{\mathrm{H}}_2\mathrm{O}+9{\mathrm{H}}_2\mathrm{O} \\ \mathrm{Sodium}\mathrm{carbonate}\mathrm{Sodium}\mathrm{cabonate} \\ \mathrm{decahydrate}\mathrm{monohydrate} \\ (\mathrm{Crystalline}\mathrm{salt})(\mathrm{White}\mathrm{amorphous}\mathrm{powder}) \end{gathered}$$

The phenomenon exhibited by washing soda is called efflorescence.