Equilibrium Representation & Calculations (College Board AP® Chemistry)

Ba²⁺(aq)  + EDTA⁴⁻ (aq)   Ba(EDTA)²⁻(aq)                         K = 7.7 x 10⁷

The polyatomic ion C₁₀H₁₂N₂O₈⁴⁻ is commonly abbreviated as EDTA⁴⁻. The ion can form complexes with metal ions in aqueous solutions. A complex of EDTA⁴⁻ with Ba²⁺ ion forms according to the equation above. A 50.0 mL volume of a solution that has an EDTA⁴⁻(aq) concentration of 0.30 M is mixed with 50.0 mL of 0.20 M Ba(N0₃)₂  to produce 100.0 mL of solution.

Considering the value of K for the reaction, determine the concentration of Ba(EDTA)²⁻(aq)  in the 100.0 mL of solution. Justify your answer.

The solution is diluted with distilled water to a total volume of 1.00 L. After equilibrium has been reestablished, is the number of moles of Ba²⁺(aq) present in the solution greater than, less than, or equal to the number of moles of Ba²⁺(aq) present in the original solution before it was diluted? Justify your answer.