# Chemistry: Stoichiometry

## 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 doesnt seem right, did i do something wrong here?

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

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? isnt it just 0.596g as given?

0.596/23.63?

Borek
Mentor
Empirical weight = molar weight of empirical formula.

Last edited by a moderator:
Empirical weight = molar weight of empirical formula.

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

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

Last edited by a moderator:
0.596 is not molar weight of empirical formula. It is weight of the sample.

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ok so how do i find the empirical weight then?

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