Chemistry: Stoichiometry

[dracolnyte]

Homework Statement

a sample of gas compound is made up only of B and H weighing 0.596g occupies 484 mL at STP. *then burned in excess O2, it yields 1.17g of H₂O and all of the boron is converted to B₂O₃
what is a) its empirical formula? b) its molecular weight? c) its molecular formula? d) the weight of B₂O₃ produced?

The Attempt at a Solution

I kinda have an idea on how to solve this, i answered a) and b), which turns out to be
2BH₂ and the molecular weight is 23.6378.

Now, I know that the molecular formula is just the empirical formula times an integer, and that integer is usually the molecular weight of the compound divided by 23.6378.

So i should be getting 0.596g/23.6378g? that doesn't seem right, did i do something wrong here?

 

[Bohrok]

You need to divide the molecular weight by the empirical weight; that gives you the integer you multiply with the empirical formula.

 

[dracolnyte]

You need to divide the molecular weight by the empirical weight; that gives you the integer you multiply with the empirical formula.

Ya I know, I have found the molecular weight, but how do i find the empirical weight? isn't it just 0.596g as given?

0.596/23.63?

 

[Borek]

Empirical weight = molar weight of empirical formula.

 

[dracolnyte]

Empirical weight = molar weight of empirical formula.

--
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ok so in my question, what did i do wrong?

 

[Borek]

0.596 is not molar weight of empirical formula. It is weight of the sample.

 

[dracolnyte]

0.596 is not molar weight of empirical formula. It is weight of the sample.

--
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www.titrations.info - all about titration methods

ok so how do i find the empirical weight then?

 

[Bohrok]

You said you have the empirical formula, so just add up the weight of the elements in the empirical formula.