{"knowledge_schema": {"broad_category": "Chemistry \u2192 Coordination Chemistry \u2192 Complex Ion Equilibria", "refinement": "This problem involves calculating the concentration of free calcium ions in a solution containing a calcium-EDTA complex, using the stability constant of the complex.", "specific_scope": "The focus is on determining the concentration of calcium ions in a 0.02 M Ca-EDTA solution at a specific temperature and pH, utilizing the equilibrium constant for the complex formation.", "goal": "Calculate the concentration of free calcium ions (Ca\u00b2\u207a) in the solution based on the given concentration of the complex and the stability constant."}, "summary": "This problem is rooted in coordination chemistry, specifically in the area of complex ion equilibria. It requires calculating the concentration of free calcium ions in a solution containing a calcium-EDTA complex, given the stability constant (KCa-EDTA) and the initial concentration of the complex. The goal is to apply the equilibrium expression related to the formation of the complex to find the concentration of free calcium ions, which is determined to be 6.3x10^-7 M."}