Question

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?

Answer 1

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

Explanation:

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

`Mg(s) +1/2O_2(g) stackrel(Delta)rarrMgO(s)`

And thus combustion of one equiv magnesium metal, `24.3*g`, should lead to formation of approx. `40*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 `MgO` ash is lost from the crucible. Be careful and don't burn yourself on the crucible.