Mass of Oxygen : 18.8 g
<h3>Further explanation</h3>
Reaction(balanced) :
4Fe + 3O₂ → 2Fe₂O₃
mass Fe = 43.7 g
mol Fe(MW= 55,845 g/mol) :

mol O₂ : mol Fe = 3 : 4, so mol O₂ :

Mass O₂(MW=32 g/mol) :

Or simply you can Conservation of mass, where the masses before and after the reaction are the same
<em>mass reactants=mass products</em>
mass iron+mass oxygen=mass iron (III) oxide
43.7 g + mass oxygen=62.5 g
mass oxygen = 62.5 - 43.7 = 18.8 g
2. Chemical because it can’t change back
3. Physical because it can be changed
Chlorine: gain, -1 charge.
iron: lose, +2 charge.
sulfur: 6, gain, -2 charge.
copper: lose, +1 charge.
The formula mass of potassium chloride is 122.55 g!
I hope this helped! Mark me Brainliest! :) -Raven❤️