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Acid Strength and Conjugate Bases

  1. Mar 3, 2006 #1
    1. Which Bronsted-Lowry acid has the strongest conjugate base?

    a. HBr
    b. HClO4
    c. HF
    d. HI

    2. What is the strongest acid among the following?

    a. HF
    b. HCl
    c. HBr
    d. HI

  2. jcsd
  3. Mar 3, 2006 #2


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  4. Mar 3, 2006 #3
    Number two is incorrect. The higher the electronegativity of X in HX, the stronger the acid. However, an exception to this is fluorine, which is the point of the question. Following this, what do you think the answer is?
  5. Mar 5, 2006 #4
    According to my text, the size of X increases from F to I, so acidity increases from HF to HI since the H-X bond strength decreases as you go down the group.

    Therefore, shouldn't my answer be correct? HI is stronger than the other three?

    If the elements of binary acids were in the same ROW, then increasing electronegativity indicates higher acid strength.
    Last edited: Mar 5, 2006
  6. Mar 5, 2006 #5


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    Yes, you are right.

    For the first one, you need to find the weakest acid (weaker the acid, stronger the conjugate base).
  7. Mar 5, 2006 #6
    I apologize. My teacher must've made a mistake when he taught us that (he only mentioned it a few times in class). I will have to talk to him about that tomorrow.
  8. Mar 6, 2006 #7
    Well, HF is the weakest acid, so my answer is correct for #1?
  9. Mar 6, 2006 #8


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    Yes, I think that's right as well.
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