Chapter 3, Problem 72QAP

A student prepares phosphorous acid, H₃PO₃, by reacting solid phosphorus triiodide with water.

${\text{PI}}_{\text{3}}\left(s\right)+{\text{3H}}_{\text{2}}\text{O}\left(l\right)\to {\text{H}}_{\text{3}}{\text{PO}}_{\text{3}}\left(s\right)+\text{3HI}\left(g\right)$ The student needs to obtain 0.250 L of ${\text{H}}_3{\text{PO}}_3\left(d=1.651\text{g}/{\text{cm}}^{\text{3}}\right)$. The procedure calls for a 45.0% excess of water and a yield of 75.0%. How much phosphorus triiodide should be weighed out? What volume of water $\left(d=1.651\text{g}/{\text{cm}}^{\text{3}}\right)$ should be used?