Answer:
0.171 grams of oxygen combined with the metal.
Explanation:
[tex]2Mg+O_2\rightarrow 2MgO[/tex]
Mass of magnesium oxide produced = 0.421 g
Mass of magnesium metal used = 0.250 g
Suppose reaction completely converts the magnesium into magnesium oxide.
Mass of oxygen combined with magnesium = m
0.421 g = 0.250 g + m
m = Â 0.421 g - 0.250 g = 0.171 g
0.171 grams of oxygen combined with the metal.