# When heated in a crucible, magnesium metal reacts with oxygen from the air to form magnesium oxide in a synthesis reaction. How do you expect the mass ofthe crucible and its contents to change after the reaction?

Jun 8, 2017

The mass of the crucible is constant. The mass CONTAINED by the crucible will increase..........

#### Explanation:

We can represent the oxidation so..........

$M g \left(s\right) + \frac{1}{2} {O}_{2} \left(g\right) \stackrel{\Delta}{\rightarrow} M g O \left(s\right)$

And thus combustion of one equiv magnesium metal, $24.3 \cdot g$, should lead to formation of approx. $40 \cdot g$ magnesium oxide. And thus the mass contained by the crucible should almost double.

Often when you do the experiment, you lose some of mass, i.e. the $M g O$ ash is lost from the crucible. Be careful and don't burn yourself on the crucible.