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Homework Help: The Empericial Formula

  1. Oct 29, 2005 #1

    When 2.435g of Antinomy is heated with excess sulfur, a chemical reaction occurs. The excess sulfur is driven off, leaving only the compound. If 3.397g of the compound are prduced, what is the empricial formula of the compound?

    :frown: I am not even sure where to begin with this question because we were only given examples of how to do the empirical formuala when given the masses of each compound. Could someone please give me a hand of hwo to get started! Thank you
  2. jcsd
  3. Oct 29, 2005 #2
    Antimony is an element, not a compound. It's trivial, but it may be important if you are asked this.

    Anyway, the trick here is to convert all the weights (that was expressed in grams), including the mass of sulfur in the "compound", to their respective mole amounts. You'll understand this was easy part of the question when you are acutally making the "empirical" formula of said "compound"

    good luck!
    Last edited: Oct 29, 2005
  4. Oct 29, 2005 #3
    I am not understanding how I am supposed to covert the weight of sulfur in the compound if I don't know what the compound is. Is is Antimony + Sulfur? And if it is, how am I supposed to know what the charge of Antimony is?
  5. Oct 30, 2005 #4
    You are making it more complicated than it should. You don't have to "know" the compound to find the wieght of sulfur in the compound, you can do this in another very familiar way, which is called the law of conservation of mass and the empirical formula. The problem mentions these clues.

    1. The antimony "in our box" reacts with "excess" sulfur.
    2. The "excess" sulfur is then driven out.
    3. Only the compound "in our box" remains.

    Do you remember the law of conservation of mass?
  6. Oct 30, 2005 #5


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    extraordinarygirl, to clarify what Umabel is saying, there's an assumption you need to make in solving this problem that should help a lot. Since it says antimony is reacted with excess sulfur, you can assume that ALL of the antimony is in your final product. Therefore, any additional mass in the final compound is due to the sulfur in the compound. That should help figure out how to calculate the number of moles of reactants and products.
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