Answer
144.564 grams
Exlanation
The given moles of MgO = 3.500 moles
The mass in grams of MgO can be calculated using the mole formula.
[tex]Mole=\frac{Mass}{Molar\text{ }mass}[/tex]From the periodic table, the atomic masses of (O = 15.999, Mg = 24.305)
Molar mass of MgO = (24.305 + 15.999) = 40.304 g/mol
Putting mole = 3.500 mol and molar mass = 40.304 g/mol into the mole formulag/mol
[tex]\begin{gathered} 3.500\text{ }mol=\frac{Mass}{40.304\text{ }g\text{/}mol} \\ \\ \Rightarrow Mass=3.500\text{ }mol\times40.304\text{ }g\text{/}mol=144.564\text{ }grams \end{gathered}[/tex]Therefore, the grams of magnesium oxide (MgO) that are in 3.500 moles of magnesium oxide = P144.564 grams