[iaoveladamaa]

This is a very simple question I know .. but I dont know how to word what I'm thinking .. so I was wondering if someone could help me.

How would your results have been different had you not cleaned the magnesium ribbon before you used it?



(In the experiment what we did was we put a piece of magnesium ribbon in 100mL graduated cylinder of HCl (15 mL of 6mol/L) and water)

[Yggdrasil]

Well what is the purpose of cleaning the magnesium ribbon?  Is the outside of the metal magnesium or has something happened to the outside?  What happens to the outside of metals over time?

[vhpk]

Perhaps there is MgO outside the Magnesium ribbon like Al₂O₃ outside the aluminium ribbon, so the result is that the volume of H₂ we get isn't similar to the result which we got by theory

[Yggdrasil]

Yup, there is a magnesium oxide (MgO) coating on the outside of the magnesium ribbon.  Although  I'm not sure that the presence of this coating will affect your calculations, MgO won't react with the HCl.  So, if the coating is thick enough, it can significantly slow the reaction of the magnesium metal below the MgO with the HCl.

[Borek]

MgO won't react with the HCl.

My books tell me that it can even react slowly with water (especially if powdered). Also if it will not react with acid it won't work in antacids when treating heartburn.

IMHO it will react, just without H₂ evolution. That will change hydrogen volume per magnesium ribbon mass ratio.