Question

Explain how anhydrous Cobalt chloride can be used in the detection of water.

Answer 1

Water test:

• There are many ways through which we could test the presence of water in any compound. One of those ways could be using the Cobalt chloride(${\mathrm{COCl}}_2$) paper test.

Material required:

• Cobalt chloride paper (dry)
• Dropper
• An unknown substance

In this method,

• A Cobalt chloride paper is taken in a desiccator and kept dry and blue.
• Then through the dropper, the unknown substance is fed to Cobalt chloride which is blue in color.
• The blue-colored paper then turns to pink.

Reaction:

$$\begin{gathered} \underset{\left(\mathrm{Blue}\right)}{\underbrace{{\mathrm{CoCl}}_2\left(\mathrm{s}\right)}}+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to \underset{\mathrm{Pink}}{\underbrace{{\mathrm{CoCl}}_2.2{\mathrm{H}}_2\mathrm{O}}\left(\mathrm{s}\right)} \\ (\mathrm{Cobalt}\mathrm{chloride})\left(\mathrm{Water}\right)\left(\mathrm{Cobalt}\right(\mathrm{II})\mathrm{chloride}\mathrm{dihydrate}) \end{gathered}$$.