I got 0.5 mol
8g/(16g/mol) = 0.5 mol
but why is the answer 0.25 mol
Calculate the number of mole of atom in 8g of oxygen gas (relative atomic mass for oxyegn: 16g/mol)?
2018-06-24 9:53 pm
回答 (5)
2018-06-25 12:25 am
✔ 最佳答案
Molar mass of O atoms = 16 g/molNo. of moles of O atoms = (8 g) / (16 g/mol) = 0.5 mol
Molar mass of O₂ = 16 × 2 g/mol = 32 g/mol
No. of moles of O₂ molecules = (8 g) / (32 g/mol) = 0.25 mol
2018-06-24 10:03 pm
moles OF ATOMS is the key here.
try this
.. 8g O2.. 1 mol O2.. .. .. ..2 mol O atoms
---- ----- x ---- ---- --- x --- ---- ----- --- --- ---- ---- = 0.5 mol O atoms
.. .. 1.. ... .. 32g O2.. .. 1 mol O2 molecules
if you asked for moles of O2 molecules, the answer would be 0.25 mol
try this
.. 8g O2.. 1 mol O2.. .. .. ..2 mol O atoms
---- ----- x ---- ---- --- x --- ---- ----- --- --- ---- ---- = 0.5 mol O atoms
.. .. 1.. ... .. 32g O2.. .. 1 mol O2 molecules
if you asked for moles of O2 molecules, the answer would be 0.25 mol
2018-06-25 9:11 am
A molecule of oxygen is O2, not just O. Therefore, the molar mass is 32, not 16. And that's why 8 grams is 1/4 mole, not 1/2 mole.
2018-06-24 10:08 pm
Do you mean atoms or molecules of O? There are 0.5 moles of O atoms (8 g / 16 g/mole = 0.5 mole), but only 0.25 moles of O2 molecules. There are two O atoms in a molecule of O2 (for every mole of O atom, there is only half a mole of O2 molecules). This does not quite match what you say in your question.
2018-06-24 10:05 pm
Because Oxygen gas is made of O2 molecules. (32g/mol).
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