The reaction produces calcium oxalate (CaC₂O₄), which is a white, insoluble solid.

Here's the balanced chemical equation:

(NH₄)₂C₂O₄ (aq) + Ca²⁺ (aq) → CaC₂O₄ (s) + 2NH₄⁺ (aq)

This reaction is often used in analytical chemistry to determine the concentration of calcium ions in a solution.