Chapter 5, Problem 100E

The oxides of Group 2A metals (symbolized by M here) react with carbon dioxide according to the following reaction:

$\text{MO}\left(s\right)+{\text{ CO}}_{\text{2}}\left(g\right)\to {\text{ MCO}}_{\text{3}}\left(s\right)$

A 2.85-g sample containing only MgO and CuO is placed in a 3.00-L container. The container is filled with CO₂ to a pressure of 740. torr at 20.°C. After the reaction has gone to completion, the pressure inside the flask is 390. torr at 20.°C. What is the mass percent of MgO in the mixture? Assume that only the MgO reacts with CO₂.