When magnesium nitrate, $\text{Mg(NO}_3)_2$, is heated, it breaks down to form a white solid together with a mixture of gases. One of the gases given off is an oxide of nitrogen, $X$. $7.4\,\text{g}$ of anhydrous magnesium nitrate is heated until no further change occurs. What mass of $X$ is formed?
- A$1.5\,\text{g}$
- B$2.3\,\text{g}$
- C$3.0\,\text{g}$
- D$4.6\,\text{g}$