Final answer:
Evaporation of a magnesium chloride mixture results in the formation of solid magnesium chloride crystals due to the removal of water, concentrating the magnesium and chloride ions into a solid ionic structure.
Step-by-step explanation:
When the mixture of magnesium chloride is evaporated, the water in the solution is removed, leading to the formation of solid magnesium chloride crystals. During the evaporation process, the magnesium ions (Mg2+) and the chloride ions (Cl-) come together to form a solid ionic compound due to their electrical attraction.
This process can be used in the preparation of magnesium through the reaction of seawater with calcium hydroxide, precipitating magnesium hydroxide, followed by addition of hydrochloric acid and evaporation to yield pure magnesium chloride.