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# A sample of the mineral troegerite, (UO2)3(AsO4)2 12H2O, has 1.24 1021 U atoms...?

A sample of the mineral troegerite, (UO2)3(AsO4)2 12H2O, has 1.24 1021 U atoms. How many arsenic atoms are present in this sample of troegerite?

The answer is 8.27E20. I have been working this problem for over two hours, and I can't figure it out please help!!!

Also, the same issues with the following question:

For the reaction CH4(g) + 2O2(g) → CO2(g) + 2H2O(l), what mass of methane (CH4) is required to react completely with 2.79 × 1024 molecules of O2?

Everything I do keeps giving me a wrong answer! please help! T.T I am so frustrated and confused! :(

### 3 Answers

- GerryLv 610 years agoFavorite Answer
(UO₂)₃(AsO₄)₂●12H₂O

In each mole of uranium dioxide (UO₂), there is one mole of uranium. In addition, in each mole of arsenic tetroxide (AsO₄), there is one mole of arsenic. Since there are three moles of uranium dioxide and two moles of arsenic tetroxide in each mole of troegerite, this means that there are three moles of uranium for every two moles of arsenic.

Divide the number of uranium atoms by the number of atoms in one mole:

1.24 x 10^21 atoms U x (1 mol / 6.022 x 10^23 atoms) = 0.00206 mol U

Convert the number of moles of uranium to the number of moles of arsenic:

0.00206 mol U x (2 mol As / 3 mol U) = 0.00137 mol As

Finally, multiply the number of moles of arsenic by the number of atoms in one mole:

0.00137 mol As x (6.022 x 10^23 atoms / 1 mol) = 8.26 x 10^20 atoms As

There are indeed eight-hundred twenty-six quintillion arsenic atoms in this sample of troegerite.

CH₄ (g) + 2O₂ (g) → CO₂ (g) + 2H₂O (l)

Convert the number of molecules of O₂ into moles of O₂

2.79 x 10^24 molecules O₂ x (1 mol O₂ / 6.022 x 10^23 molecules) = 4.63 mol O₂

One mole of methane reacts with two moles of diatomic oxygen, so:

4.63 mol O₂ x (1 mol CH₄ / 2 mol O₂) = 2.32 mol CH₄

Finally, convert moles of methane to mass of methane in grams:

2.32 mol CH₄ x (16.04 g CH₄ / 1 mol CH₄) = 37.2 g CH₄

Thirty-seven and two-tenths grams of methane are required to react completely with 2.79 x 10^24 molecules O₂.

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- XemystLv 410 years ago
1.)

(UO2)3(AsO4)2*12H2O

There are 3 atoms of U and 2 atoms of As

in every molecule of troegerite.

The number of As-atoms is equal

the number of U-atoms multiplyed on 2/3

n(As)=1,24*10^21*(2/3)=8,26(6)*10^20 atoms

2.)

CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)

Mu(O2)=2,79*10^24:(6,022*10^23)=4,633 mol

Mu(CH4)=Mu(O2):2=2,3175 mol

m(CH4)=2,3175*16=37,08 g

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- 4 years ago
not something. you will not be able to. He did not have one. abdomen buttons are in basic terms on those that are BORN. not on those that are CREATED. it is what's left over from the umbilical cord of the mum. Adam did not have a mom.

- Waheed3 years agoReport
wtf

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