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Limiting Reagent Question

  1. Nov 10, 2011 #1
    I have some doubts in determining the limiting reagent in a question

    Based on my understanding, I will explain how I found out the limiting reagent in this problem. Please tell me if my explanation is correct or not.

    Equation : Zn + 2HCl - ZnCl2 + H2

    To determine the limiting reagent, we need to see how much ZnCl2 will Zn and HCl produce separately.
    65.4g of Zn gives 136.4g of ZnCl2
    Thus 1g of Zn will give 2.08g of ZnCl2

    73g of HCl gives 136.4g ZnCl2
    Thus 1g of HCl will give 1.86g of ZnCl2

    Now the limiting reagent is the one which produces the least amount of ZnCl2

    Thus in this equation, HCl is the limiting reagent.

    please tell me if my explanation is correct or not.
    Please help!!!!
  2. jcsd
  3. Nov 10, 2011 #2
    It has been a long time since I've done a question like this, but are limiting reagent questions to be done in terms of mass or in terms of moles? If they are in terms of moles then you have a problem because you'll need to know how many moles of 2HCl you need.
  4. Nov 10, 2011 #3


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    Staff: Mentor

    First of all - limiting reagent exists only if amounts of reactants are given. So if the question is "if you react 1g of Zn with 1g of HCl, which one is a limiting reagent" - you can calculate an answer. But if the question is "which is the limiting reagent if you mix Zn with HCl" - it doesn't make sense.

    In other words - limiting reagent is not a "property" of the reaction.
    Last edited: Nov 10, 2011
  5. Nov 10, 2011 #4


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    Homework Helper
    Gold Member

    Borek beat me to it so I leave it in his good hands.

    As often here we are given an answer and have to work out what is the question; we are not too bad at it. :biggrin:
  6. Nov 10, 2011 #5
    Thankyou so much :)
    You guys rock! :D
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