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

In summary: In this case, it would be 2*B = 2*10.81 = 21.62 and 4*H = 4*1.008 = 4.032, so the empirical weight is 25.652 g/mol. In summary, the sample of gas compound made up of B and H weighs 0.596g and occupies 484 mL at STP. When burned in excess O2, it yields 1.17g of H2O and all of the boron is converted to B2O3. The empirical formula is 2BH2 and the molecular weight is 23.6378 g/mol. To find the molecular formula, the molecular weight must be divided by the
  • #1
dracolnyte
28
0

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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  • #2
You need to divide the molecular weight by the empirical weight; that gives you the integer you multiply with the empirical formula.
 
  • #3
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?
 
  • #4
Empirical weight = molar weight of empirical formula.
 
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  • #6
0.596 is not molar weight of empirical formula. It is weight of the sample.
 
Last edited by a moderator:
  • #8
You said you have the empirical formula, so just add up the weight of the elements in the empirical formula.
 

What is stoichiometry?

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in a chemical reaction. It involves using mathematical equations to determine the amounts of substances involved in a reaction.

What is a mole in chemistry?

A mole is a unit of measurement in chemistry that represents a specific number of particles. One mole is equal to 6.022 x 10^23 particles, which is known as Avogadro's number. This number is used to convert between mass and number of particles in chemical reactions.

How do you calculate the limiting reactant in a chemical reaction?

The limiting reactant is the substance that is completely used up in a chemical reaction, thereby limiting the amount of product that can be formed. To calculate the limiting reactant, you must first determine the moles of each reactant present, then use the balanced chemical equation to determine which reactant will run out first.

What is a percent yield in chemistry?

Percent yield is a measure of the efficiency of a chemical reaction. It is calculated by dividing the actual yield (the amount of product obtained in an experiment) by the theoretical yield (the amount of product that should be obtained based on stoichiometric calculations) and multiplying by 100. A 100% yield means that all of the reactants were converted to product.

How does stoichiometry relate to the conservation of mass?

Stoichiometry is based on the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. This means that the total mass of the reactants must be equal to the total mass of the products. Stoichiometric calculations use this principle to determine the amounts of reactants and products involved in a reaction.

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