[polar8]

Hi there!

We just had a lab in which we heated magnesium pieces in a crucible over a burner, and observed the reaction. I loved the lab but I have three questions!

1. We were instructed to perform the lab with the crucible lid slightly to the side. Why was this instructed?
2. What were two purposes for cutting the magnesium ribbon?
3. What is the vapor/gas that escaped during the reaction?

Thanks alot for your *delete me*

[polar8]

Anyone?

[enahs]

Well, what are you thoughts as to why?

[agrobert]

1. Possible so that you could observe the reaction and to supply adequate oxygen.

2. Increase surface area, better ignition of smaller pieces.

3. 2 Mg⁰_(s) + O_2(g) --> 2 MgO (s) + heat
vapor or gas may be steam from water in the air

[Sev]

3. 2 Mg⁰_(s) + O_2(g) --> 2 MgO (s) + heat
vapor or gas may be steam from water in the air

Or maybe from rxn of Magnesium nitride with moisture in crucible?

[LQ43]

were you told to heat it very slowly? but I bet this was hard to do and the Mg ignited and gave off the smoke/vapor.  Some of the MgO that is formed escapes in the form of fine powder, why the smoke was white. Ideally the oxidation is supposed to go slowly to reduce this loss that occurs from the ignition. It would be best to cover the crucible completely to prevent loss of the powder, but agrobert is right that you also need enough oxygen.

(the crucible is heated well above the boiling point of water, so there is no moisture in the crucible by the time the oxidation occurs)

the reaction of Mg + N2 to Mg3N2 is a major byproduct  - did your product look yellowish/greenish? if so then alot of the MgO that you were supposed to make went up in smoke!