Using stoichiometry to determine empirical formula

In summary, the given conversation discusses the reaction between 1.000 g of vanadium and 8.000 g of bromine, resulting in leftover bromine and a compound containing both elements. The excess bromine is then used in a second reaction to produce a mixture containing 2.93 g of sodium sulfate. By using the given information, we can determine the empirical formula of the compound formed by finding the moles of vanadium and bromine in the first reaction. The final result is VBr3.
  • #1
littlebearrrr
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Homework Statement


1.000 g of vanadium is mixed with 8.000 g of bromine. After the elements react, some bromine is left over, along with a single compound that contains the two elements. The excess bromine is removed and allowed to react with excess sodium sulfite and excess sodium hydroxide, producing a mixture that contains 2.93 g of sodium sulfate. The balanced equation for this second reaction is:

2NaOH + Na2SO3 + Br2 -> 2NaBr + Na2SO4 + H2O

Based on this info, determine the empirical formula of the compound that was formed when vanadium reacted with bromine.


Homework Equations



None.

The Attempt at a Solution



Well, I know that my endgoal here is to find the moles of vanadium and moles of bromine for the product in the first reaction. Once I get there, I'm pretty much all set to go.

To start, I used the given amount of vanadium/bromine to find moles of vanadium/bromine. Since I know vanadium is the limiting reactant, I used my calculated moles of bromine (left over) to find the amount of bromine left over from the reaction. At this point, I was unsure what to do next. Mostly, I am confused about what I need to do with the given amount of sodium sulfate (and how the second reaction is relevant to the problem).
 
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  • #2
The second equation tells you how much Br was left over after reacting completely with V. You can subtract the excess amount from the original amount to find the amount of Br that reacted. From here you can find molar ratio of V and Br using the amount of V reacted and the amount of Br reacted.
 
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  • #3
Thanks for the response! I got VBr3.

Steps:
grams of sodium sulfate -> moles of sodium sulfate -> moles of Br2 -> grams of leftover Br2

Subtract this from the original amount to obtain grams of Br2 that reacted in the first reaction. Now that we have amount of grams that reacted for both vanadium and bromine, we can find the moles for each to obtain the e. formula.

Thanks again :)
 

Related to Using stoichiometry to determine empirical formula

1. What is the purpose of using stoichiometry to determine empirical formula?

Stoichiometry is used to calculate the quantitative relationships between reactants and products in a chemical reaction. By using stoichiometry, we can determine the empirical formula, which shows the simplest whole number ratio of elements in a compound.

2. How do you calculate the empirical formula using stoichiometry?

To calculate the empirical formula using stoichiometry, we need the mass or percentage composition of each element in the compound. Then, we convert the masses to moles and divide by the smallest number of moles to get the mole ratio. The mole ratio represents the empirical formula.

3. Can stoichiometry be used to determine the molecular formula?

No, stoichiometry can only determine the empirical formula, which does not provide information about the actual number of atoms in a molecule. To determine the molecular formula, additional information such as the molar mass of the compound is needed.

4. What are the limitations of using stoichiometry to determine empirical formula?

Stoichiometry assumes that reactions occur in perfect conditions and that all reactants are completely consumed. In reality, some reactions may not go to completion and impurities may be present, affecting the accuracy of the results.

5. Are there any real-life applications of using stoichiometry to determine empirical formula?

Yes, stoichiometry is used in many industries such as pharmaceuticals, food production, and environmental monitoring to ensure the correct amounts of reactants are used and to determine the composition of the final product.

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