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chem ques

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AN10:
can anybody plz solve this ques for me...i thnk im solving it wrong because my ans is weird (in decimals)

A hydrated aluminium sulfate, Al2(SO4)3. xH2O, contains 8.20% of aluminium by mass. Find the value of x.

Ghost Of Highbury:
ok...i too am getting a wierd answer

mss of elements - Al - 17

S - 32
O - 16
H - 1

mass of elements in the hydrated salt

Al- 54
S - 96
O - 192
and water = 18x

==>

first find the total mass

54 / total *100 = 8.2

5400/ total = 8.2

total = 5400 / 8.2 = 658.53

therefore 54 + 96 + 192 + 18x = 658.53

18x = 316.53

x = 17.585

AN10:
i got da same ans....anywayz Thanks!!

Ghost Of Highbury:

--- Quote from: AN10 on September 09, 2009, 05:58:22 pm ---i got da same ans....anywayz Thanks!!

--- End quote ---
welcome..
.
is the question correct??
i mean..is it exact 8.2%

nid404:
 u write the decimal as a whole numbers...so this becomes 18 H2O
never leave ur answer in decimals for such questions...always round it off to the nearest whole no.

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