[Jade]

Okay I've been trying to figure out this question for several minutes. I guess I have just forgotten how to do it. If anyone could help it would be greatly appreciated.

A mass of 3.1442 grams of an unknown metal reacts with oxygen to give 4.050 grams of an oxide of the type EO. What is the atomic mass of the unknown element? What is the unknown element?

[DrCMS]

To solve work out how much oxygen is in the oxide get it as grams to begin with and then convert it to moles.  Once you have that given that the oxide is MO you have the same number of moles of metal as oxygen.  Once you have the number of moles of the metal plus the weight of original metal you can work out it's atomic weight and then which metal it is.