{"knowledge_schema": {"broad_category": "Chemistry \u2192 Coordination Chemistry \u2192 Complexation Equilibria", "refinement": "This problem involves the equilibrium between a metal ion complex and its free ligand in solution, specifically focusing on the behavior of EDTA in a buffered solution at a specific pH.", "specific_scope": "The task is to calculate the concentration of free EDTA ions in a solution containing a known concentration of the Ca-EDTA complex, taking into account the stability constant and the fraction of EDTA in its deprotonated form at the given pH.", "goal": "Determine the concentration of free EDTA ions in the solution using the provided equilibrium constant and the fraction of EDTA in the Y^4- form."}, "summary": "This problem is rooted in coordination chemistry, specifically the equilibrium dynamics of metal-ligand complexes. It requires calculating the concentration of free EDTA ions in a solution where a stoichiometric Ca-EDTA complex is present, given the stability constant and the fraction of EDTA in its deprotonated form at pH 10. The goal is to apply the equilibrium expression to find the concentration of free EDTA ions, leading to the answer of 2.0x10^-6 M."}