Question

How many grams of O₂ are required to produce 358.5 grams of ZnO? 

2Zn + O₂ --> 2ZnO

Answer 1

Moles of $Zno$ $=\frac{358.5}{81.38}=4.41moles$

Moles of $O_2=\frac{4.41}{2}=2.205 moles$

Mass of $O_2= 2.205×16= 35.28g$