Question

when a certain compound was heated in a test tube, it changed from red to blue and water formed on the colder parts of the test tube. solutions of both the original salt and the residue were pink. is the compound a true hydrate or not? briefly explain your answer

Answer 1

# Cobalt (II) chloride hexa hydrate is red in color in a solid state.

# If we heat the salt . dehydration takes place.

#Therefore , color change takes place due to change in geometry

#Aqueous solutions of both CoCl₂ and the hydrate contain the species [Co(H₂O)₆]²⁺

# [Co(H₂O)₆]²⁺   - Pink colour

The above equilibrium reaction is weakly endothermic, D_rH^o > 0 which means that heat is absorbed during this substitution process. According to the Le Chatelier’s principle, if a chemical dynamic equilibrium is disturbed by changing the conditions (concentration, temperature, volume or pressure), the position of equilibrium moves to counteract the imposed change. If we apply the Le Chatelier’s principle to this particular case, we can conclude that heating the pink hexaaquacobalt(II) complex will shift the equilibrium to the right, in order to absorb this energy. During this equilibrium shifting bluetetrachlorocobaltate(II) complex is formed. Contrary, cooling down the hot solution leads to the blue complex decomposition and formation of pink hexaaquacobalt(II) complex – the reaction is reversible.