In an experiment 2.750 g of magnesium is reacted with 2.571 g of oxygen gas according to the equation:

Question

Mg + O2 ==> MgO.
What mass of the other reactant is in exess?

You need equal number of moles of each. Which has the excess?

moles Mg=2.750/molmassMg

moles O2=2.571/32

One will have more than needed.(30*1.50)D+ (70+35)I=25500(30*1.50)D+ (70+35)I=25500