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Homework Help: Is there any formula for this kind of chemistry problem?

  1. Sep 29, 2009 #1
    I am suffering from this kind of chemistry problems. I think I will have bunch of these in my exam. But I can't understand this kind of problem's solutions. If you know any formula or information about this, please help.

    How many grams of fluorine gas must react to give 9.26 g of sulfur hexafluoride?
    What mass of calcium chloride is required to react completely with 5.00 g of sodium phosphate?
    How many grams of oxygen gas must react to give 6.85 g of calcium oxide?
    type of problem: how many [gram/mole] must [react/be needed] to [produce/give] x gram of p?

    The official state of this problem is called [calculate amounts of reactants for a reaction in grams or moles]

    You do not have to answer to these problems. But if you can give me some procedures about how the answer can be derived, I would appreciate it, because I want to know kind of formula, equation to plug values in it.

    What I tried is to divide the weight I am given with the formula weight of something...can't go further. Please help.
  2. jcsd
  3. Sep 29, 2009 #2
    I will try to explain it to you with a pretty simple equation.
    By knowing the balanced chemical equation, you know the mole proportion between the reactants and the products. In our example, for each mole of O2 you get twice that amount of H2O moles.

    Everything has to be calculated in moles, so if the problem gives you the mass of a reactant or product, you simply convert mass to moles using the molar mass of the compound or viceversa.
  4. Sep 30, 2009 #3


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