[Julie Smith]

hi,

I have a question regarding figuring out molar mass of two different elements. I know that in order to find the atomic mass of magnesium via an experiment you can either determine the number of moles of acid that are consumed or you have to determine the number of moles of hydrogen gas produced by a known mass of magesium. I was wondering if any of those methods could work to find the molar mass of copper, preferably the second one i mentioned? If so, can someone please tell me why I can use the same method to find the molar mass of copper that I did to find magnesium?

Oh, by the way, the reaction used is: Mg + 2H   ---> Mg(2+) + H2

Thanks.

[enahs]

Mg _(s) + 2 H₂O _(g) → Mg(OH)_{2 (s)} + H_{2 (g)}


Copper does not react with water as such. Copper metal is not super reactive, hence why it is used in so many products.

However, there are many Compounds in which copper is a part, and many ways to determine the amount. A common one is the Iodometric determination of Copper. Here are a couple of pages.
http://www.csudh.edu/oliver/demos/hh-cubr/hh-cubr.htm
http://www.cofc.edu/~kinard/221LCHEM/CHEM221L%20Iodometric%20Copper%20Determination.htm


Of course, if you have a pure element, you can just take its mass....

[Julie Smith]

thanks enahs!

I actually have another question if anyone can help me with it. In my experiment, I'm trying to find the atomic mass of magnesium, but what would happen if all the pieces of magnesium I use are covered in a thin layer of magnesium oxide? Would this affect the accuracy or precision of my experimental value for the atomic mass? For example, would it cause my atomic mass to be higher or maybe lower than the actual value?

thanks.