Both calcium oxide and magnesium sulfide react with acid. $\text{CaO}(\text{s}) + 2\text{H}^+(\text{aq}) \rightarrow \text{Ca}^{2+}(\text{aq}) + \text{H}_2\text{O}(\text{l})$ $\text{MgS}(\text{s}) + 2\text{H}^+(\text{aq}) \rightarrow \text{Mg}^{2+}(\text{aq}) + \text{H}_2\text{S}(\text{g})$ A sample of these two compounds, $X$, is reacted with exactly $0.125\,\text{mol}$ of dilute hydrochloric acid. The quantity of hydrogen sulfide produced is $0.0250\,\text{mol}$. What mass of calcium oxide was in mixture $X$?
- A$1.4\,\text{g}$
- B$2.1\,\text{g}$
- C$2.8\,\text{g}$
- D$4.2\,\text{g}$