Javier forgot to polish the magnesium metal. Will the reported mole ratio of magnesium to oxygen be too high or too low as a result of his mistake? Explain.

Before polishing, the material will be Magnesium oxide. This will be heavier than if it were only magnesium. Therefore, in the equation:

moles = mass / Mr

The numerator would be bigger, meaning a value of moles that is too high will be reported.

When the moles of Mg will be too high, the ratio of Mg to O will also be too high.