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what got wrong in this problem?

a sample of an unknown oxide of barium gave upon exhaustive heating 5 gm of pure Bao and 366 cc of oxygen gas measured at 273 k and 1 atm pressure.what is the emperical formula of the unnown oxide? what wt of oxide was present initially?
here i did the following:-
mole of barium=(366/1000/22.4)=0.01633
mole of oxygen=2*(mole of o2 )+mole of oxygen in barium
=0.03268+0.01633=0.4901
and their ratio (emperical formula)is 1:3
but here answer is 1:2
so what mistake did i make?
Original post by map06
a sample of an unknown oxide of barium gave upon exhaustive heating 5 gm of pure Bao and 366 cc of oxygen gas measured at 273 k and 1 atm pressure.what is the emperical formula of the unnown oxide? what wt of oxide was present initially?
here i did the following:-
mole of barium=(366/1000/22.4)=0.01633
mole of oxygen=2*(mole of o2 )+mole of oxygen in barium
=0.03268+0.01633=0.4901
and their ratio (emperical formula)is 1:3
but here answer is 1:2
so what mistake did i make?



How come you did that to find moles of barium? Shouldn't you divide the mass of Ba in BaO (which you find by percentage composition x 5) and divide it by the RAM of Ba?

A better way would be to set up the equation with variable coefficients and then solving it, I guess

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Reply 2
This is a decomposition, no analysis involving coefficients is necessary at all. Convert 0.366 dm3 O2 to a mass of O2 (e.g. using the ideal gas equation) and add this to the mass of your product oxide, and you get the mass of your reactant oxide. If you really want, you can work out how many moles of BaO there were, then take this as the same number of moles as in the reactant to calculate the molar mass of the reactant oxide, after which it will be easy to find the stoichiometric coefficients.

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