Question

1. If the surface of the Mg ribbon you used were covered with a thin oxide coating prior to the reaction, would your product appear to be Mg-rich or Mg-poor?

Explain. The mass increase would be (greater than, less than, equal to) what pure Mg reactant would predict.

2. Select the modifications to the procedure that would be more likely to ensure that all the Mg would react completely with O2. (Select all that apply).

React in pure O2

Remove the crucible lid while heating

React under an inert atmosphere

Increase Mg surface area

Use a smaller crucible

Answer 1

1. If the surface of the ribbon is oxidised, that means some of the Mg in the ribbon cannot react as it is in the form of MgO. This would make the ribbon Mg-poor

2. We need to maximise the available Mg and therefore must heat it in an inert atmosphere.