Explain why this particular hydrate has a blue color when it has water in it yet nacl is colorless when it has water in it.?

Check explanation

Explanation:

The compound we are comparing with Sodium Chloride, NaCl here is an hydrate of Cobalt chloride, CoCl2. Cobalt chloride changes color in response to humidity. That is, as humidity increases, cobalt chloride changes color from blue to purple and then, to pink.

As Cobalt chloride absorb water, the Cobalt chloride crystal structure rearranges itself to to accept the water molecules to form a dihydrate.

The hydration reaction can be represented in equation (1) as below;

CoCl2 + 2H2O > CoCl2.2H2O.(1).

The CoCl2 is blue in colour while the CoCl2.2H2O is purple in colour.

When more water is added to the CoCl2,the crystal structure changes again in order to allow more water molecules in order to form the hexahydrate. The equation of reaction is given in the equation below;

CoCl2 . 2 H2O + 4 H2O > CoCl2 . 6 H2O