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Homework Help: Stoichiometry applied to reactions and chemical equations

  1. Feb 26, 2008 #1
    1. The problem statement, all variables and given/known data
    I don't understand this problem, i think he wants me to find the limeted reaction. If you could explain as good as possible. Thanks :smile:

    2. Relevant equations
    Al(OH)3(s) + H2SO4(l) → Al2(SO4)3(aq) + H2O(l)
    If 1.28 g of aluminum hydroxide reacts with 3.73 g of sulfuric acid, what is the mass of the water produced? (Hint: First balance the equation, then think about limiting reactants.)

    3. The attempt at a solution
    I already balanced the equation, but dont know how to start the formula
    2Al(OH)3(s) + 3H2SO4(l) → Al2(SO4)3(aq) + 6H2O(l)
  2. jcsd
  3. Feb 26, 2008 #2
    What is the limiting reactant, namely, the least moles of substance you have on the left?

    How many moles of aluminum hydroxide do you have, and how many moles of sulfuric acid you have?

    From there, perform your stoich, I assume you've been taught.
  4. Feb 26, 2008 #3
    We just started this today. I didn't really understand it in class and didn't have enough time to ask the teacher. If you have any websites or a good book that walks me through these kinds of problems, i would appreciate it very much.
  5. Feb 27, 2008 #4
    Well, first you need to find which reactant (aluminum hydroxide or sulfuric acid) produces the least amount of water. This is the limiting reagent.

    To do this, use your mol to mol ratios. Have you done that in class yet? Find mols of aluminum hydroxide. Then, using mol to mol ratio, find how many mols of water would be produced from that amount of aluminum hydroxide.

    Now find mols of sulfuric acid, and find the mols of water the same way as above.

    Which produces the least amount of water? That is going to be your limiting reagent. Once the limiting reagent is used up, the reaction can't continue, right?

    Now convert the mols of water to mass of water. Use the mols of water from the limiting reagent you found above.

    I hope this makes sense, write back, I will try to explain more clearly.
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