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# $Al_2(SO_4)_3.XH_2O$ has 8.1% aluminum by mass.The value of $X$ is

$(a)\;4\qquad(b)\;10\qquad(c)\;16\qquad(d)\;18$

Can you answer this question?

$100g$ atom has $Al=8.1g$
$\therefore 342+18x$g compound has 54g
Or Al%=$\large\frac{54\times 100}{342+18x}$$g$=8.1
$x=18$
Hence (d) is the correct option.
answered Oct 25, 2013