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

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Discussion Overview

The discussion revolves around calculating the molecular formula of a gas compound consisting of boron (B) and hydrogen (H) in the context of stoichiometry. Participants are addressing a homework problem that involves determining the empirical formula, molecular weight, molecular formula, and the weight of boron trioxide (B2O3) produced from a combustion reaction.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant proposes that the empirical formula is 2BH2 and calculates the molecular weight as 23.6378.
  • Another participant suggests that to find the molecular formula, one must divide the molecular weight by the empirical weight, which is a necessary step to determine the integer multiplier for the empirical formula.
  • There is confusion regarding the definition of empirical weight, with one participant mistakenly suggesting that it is the weight of the sample (0.596g).
  • Participants clarify that the empirical weight should be the molar weight of the empirical formula, not the sample weight.
  • One participant indicates that to find the empirical weight, one should sum the weights of the elements in the empirical formula.

Areas of Agreement / Disagreement

Participants generally agree on the method to find the molecular formula but disagree on the definition and calculation of empirical weight. The discussion remains unresolved regarding the correct approach to determining the empirical weight.

Contextual Notes

There is a lack of clarity on the assumptions regarding the empirical formula and its molar weight, which affects the calculations presented. The discussion also highlights the need for precise definitions in stoichiometric calculations.

dracolnyte
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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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