Here's why:
* The Reaction: The reaction between calcium chloride and sodium hydroxide is a double displacement reaction:
CaCl₂ (aq) + 2NaOH (aq) → Ca(OH)₂ (s) + 2NaCl (aq)
* Formation of Calcium Hydroxide: Calcium hydroxide (Ca(OH)₂) is the precipitate that forms. It's an insoluble compound in water.
* Solubility Rules: Solubility rules help predict which products will be soluble (remain dissolved) and which will be insoluble (form a precipitate).
* Most hydroxide compounds (like Ca(OH)₂) are insoluble, except for those of Group 1 elements (like Na) and Ba.
* Most chloride compounds (like NaCl) are soluble.
In Summary: When calcium chloride and sodium hydroxide react, they form calcium hydroxide, which is insoluble in water and therefore precipitates out of solution.
