* Solubility Rules: Calcium chromate (CaCrO₄) is actually soluble in water. Solubility rules in chemistry dictate that most chromates are soluble, with exceptions for some heavy metals.
* No Driving Force: Since both calcium chromate and potassium chromate are soluble, there is no driving force for a reaction to occur. Reactions generally proceed when they result in the formation of a precipitate (insoluble solid), a gas, or a weak electrolyte.
In Summary:
The lack of a precipitate formation is the primary reason why calcium ions do not react with potassium chromate.
