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Help?!

My answer to this question seems incorrect given the percentage by mass of each of the components. Have I gone wrong somewhere? Thanks!

a) Emeralds are a form of the mineral beryl, with their green colour due to the impurities present.
A sample of beryl contains 10.04% aluminium, 53.58% oxygen and 31.35% silicon by mass, with beryllium making up the remainder. Its molecular formula is Al2BexSi6O18.
Find the percentage by mass of beryllium in the compound and hence calculate the value of x in this formula.

10.04 + 53.58 + 31.35 = 94.97%
% by mass(Be) = 100 - 94.97 = 5.03%

Al - 10.04/27.0 = 0.3719/0.3719 = 1
O - 53.58/16.0 = 3.349/0.3719 = 9
Si - 31.35/28.1 = 1.116/0.3719 = 3
Be - 5.03/9.01 = 0.5583/0.3719 = 2

Empirical formula = AlBe2Si3O9

Hence, molecular formula = Al2Be4Si6O18

Value of x = 4

Reply 1

lauraMarieBrooks

Looks right to me? I'd have done exactly the same?

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Reply 2

lauraMarieBrooks

I'd say value of x is 2 though? Isn't the question asking what x is in that formula not the molecular?

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Reply 3

Borek

Strange. Percentages given are off (see the rightmost column). Perhaps they are meant to be treated as experimental values, but IMHO it should be clearly stated in the question.