How Do You Calculate the Molecular Formula of a Gas Compound in Stoichiometry?

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SUMMARY

The discussion focuses on calculating the molecular formula of a gas compound composed of boron (B) and hydrogen (H) using stoichiometry. The empirical formula determined is 2BH2, with a molecular weight of 23.6378 g/mol. To find the molecular formula, one must divide the molecular weight by the empirical weight, which is the molar weight of the empirical formula, not the sample weight of 0.596 g. The weight of B2O3 produced from the combustion of the compound is also a key consideration in the calculations.

PREREQUISITES
  • Understanding of stoichiometry principles
  • Knowledge of empirical and molecular formulas
  • Familiarity with gas laws at STP (Standard Temperature and Pressure)
  • Basic skills in chemical calculations and molar weights
NEXT STEPS
  • Learn how to calculate empirical formulas from elemental composition
  • Study the concept of molar weight and its significance in stoichiometry
  • Explore the calculation of products formed in combustion reactions
  • Investigate the use of chemical calculators for stoichiometric calculations
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Chemistry students, educators, and anyone involved in chemical analysis or stoichiometric calculations will benefit from this discussion.

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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?
 
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You need to divide the molecular weight by the empirical weight; that gives you the integer you multiply with the empirical formula.
 
Bohrok said:
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?
 
Empirical weight = molar weight of empirical formula.
 
Last edited by a moderator:
0.596 is not molar weight of empirical formula. It is weight of the sample.
 
Last edited by a moderator:
You said you have the empirical formula, so just add up the weight of the elements in the empirical formula.
 

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