How do you find how many atoms of an element are in a compound?

I need to find how many Oxygen atoms are in 1 gram of Al2(SO4)3. I have tried finding the mass percent, and working it from there, but I can’t get the right answer. Does anyone know how to solve this?

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Printed from: http://arezeez.com/2009/11/19/how-do-you-find-how-many-atoms-of-an-element-are-in-a-compound/ .
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5 Comments   »

  • basimsaleh says:

    Mole contain (6.02 x10 to the power 23) of molecules
    1 gm /molecular weight of Al2(SO4) = no. of moles in one g
    molecular weight of O2/molecular weight of the sulphate x100= percent of oxgen in one mole,
    then calculate the percent of oxgen in the moles in 1 g
    the result multiplied by 6.02 x 10 to the power 23 gives the no.of oxgen in 1 g of sulphate and then the numbers of atoms of Oxygen.

  • Azz! says:

    Look on google or ask a scientist

  • deflagrated says:

    First find the number of moles(x) = weight(1g)/(molecular weight)
    so there are x moles or Avagadro’s constant*x molecules of the Al compound. As there are 12 O atoms the answer is 12 times this value.

  • rfamilymember says:

    find the molecular weight of aluminium sulphate
    192/molecular weght of aluminium sulphate will give the weight of oxygen in 1 gm of aluminium sulphate
    first of all find the weight of oxygen in 1 gram of Al2(SO4)3
    in 32 gms of oxygen there are 6.022*10^23 molecules
    so weight of oxygen multiplied by 6.022*10^23 will give the no of molecules
    no of atoms=twice the no of molecules because oxygen is diatomic

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