Chapter 15, Problem 57QAP

Calcium ions in blood trigger clotting. To prevent that in donated blood, sodium oxalate, Na₂C₂O₄, is added to remove calcium ions according to the following equation.

${\text{C}}_2{\text{O}}_4{}^{2-}\left(aq\right)+{\text{Ca}}^{2+}\left(aq\right)\to {\text{CaC}}_2{\text{O}}_4\left(s\right)$Blood contains about 0.10 mg Ca²⁺/mL. If a 250.0-mL sample of donated blood is treated with an equal volume of 0.160 M Na₂C₂O₄, estimate [Ca²⁺] after precipitation. $\left(K_{\text{sp}}{\text{CaC}}_2{\text{O}}_4=4\times {10}^{-9}\right)$