The aluminum sulfate hydrate [Al2(SO4)3 x XH2O] contains 8.20 percent Al by mass. Calculate X, that is the number of water molecules associated with each Al2(SO4)3 unit.
2006-12-30 12:11:24 · 2 answers · asked by Luciya 2 in Science & Mathematics ➔ Chemistry
masses (g/mol):
Al: 26.98
S: 32.07
O: 16.00
H: 1.01
math:
total mass = (26.98)*2+(32.07+16.00*4)*3 + X * (1.01*2+16.00)
0.0820 * (total mass) = (26.98)*2
Solve for X
X~=18
Or wikipedia:
http://en.wikipedia.org/wiki/Aluminium_sulfate
2006-12-30 12:36:07 · answer #1 · answered by MooseBoys 6 · 0⤊ 0⤋
the mass of the hydrate : 27 *2 + (32 + 16*4) * 3 + 18*x = 342+18x
the total mass of Al atoms : 27*2 = 54g
%Al = 54 / (342 + 18x) = 8.2% = 0.082
solve for x , we have x = 17.59, round(x) = 16
thus the chemical formula of the hydrate is [Al2(SO4)3 x 16H2O]
2006-12-30 20:26:09 · answer #2 · answered by James Chan 4 · 1⤊ 1⤋