For the reaction "Fe"_2"O"_3 + 2"X" -> 2"Fe" + "X"_2"O"_3Fe2O3+2Xโ†’2Fe+X2O3, if "79.847 g"79.847 g "Fe"_2"O"_3Fe2O3 reacts with excess "X"X (FW = "159.691 g/mol"FW=159.691 g/mol for the iron(III) oxide) to yield "50.982 g X"_2"O"_350.982 g X2O3 and "55.847 g Fe"55.847 g Fe, what is the identity of "X"X?

2 Answers
Aug 18, 2017

Aluminium (Al)

Explanation:

There is a simple concept.
According to law of mass conservation,
[2X]=(55.847+50.982)-79.847=26.982[2X]=(55.847+50.982)โˆ’79.847=26.982
Here, 2Fe2Fe has a mass same as its atomic weight so as 2X2X has a mass same as its atomic weight which is 26.98226.982. This is the atomic weight of Aluminium.

Aug 19, 2017

For the reaction

"Fe"_2"O"_3 + 2"X" -> 2"Fe" + "X"_2"O"_3Fe2O3+2Xโ†’2Fe+X2O3,

convert the mass of iron(III) oxide to mols.

79.847 cancel("g Fe"_2"O"_3) xx ("1 mol")/(159.691 cancel("g Fe"_2"O"_3)) = "0.50001 mols"

"Fe"_2"O"_3 is 1:1 with "X"_2"O"_3, so "0.50001 mols" of "X"_2"O"_3 was produced. By conservation of mass,

m_"X" = m_("X"_2"O"_3) + m_"Fe" - m_("Fe"_2"O"_3)

= 50.982 + 55.847 - 79.847 "g"

= "26.982 g X"

Since "X" is 2:1 with "X"_2"O"_3, "1.00002 mols" of "X" was produced. So, its molar mass is:

"26.982 g X"/"1.00002 mols" = ul(26.981_5color(white)(.)"g/mol")

which is essentially the exact molar mass of aluminium (aluminum) atom.