If you look at the periodic table, the number under magnesium is 24.305. That means that there are 24.305 grams in every mole of magnesium. So, you can use this equation to turn 88.1 moles into grams:
\((88.1\ mol\ Mg)(\frac{24.305\ g\ Mg}{1\ mol\ Mg}) = 2141.2705\ g\ Mg\)
Therefore, in 88.1 mol Mg, there is about 2141 grams.
