A 4.78-g sample of aluminum completely reacts with oxygen to form 6.67 g of aluminum oxide. What is the mass percent composition of aluminum in aluminum oxide?
The percent composition of aluminium in the
resulting oxide will be the ratio between the mass of aluminijm and the total mass of the oxide, multiplied
#"% Al" = m_"Al"/m_"oxide" xx 100#
In your case, you know that a
unknown aluminium oxide.
Moreover, you know that this oxide has a mass of
Since all the luminium that initially reacted with the oxygen is now a part of the oxide, you can say that its
percent composition in the oxide will be
#"% Al" = (4.78color(red)(cancel(color(black)("g"))))/(6.67color(red)(cancel(color(black)("g")))) xx 100 = 71.664%#
Rounded to three sig figs, the
answer will be
#"% Al" = color(green)(71.7%)#