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Acidity and atomic size?

  1. Jul 17, 2012 #1
    Suppose I have two acids HX and HZ. Say X is smaller then Z in atomic size. So then one would think that HX would be a more stable molecule then HZ since X has a higher charge density then Z (Both have same electronegativity) . HZ being a weaker molecule would dissociate more rapidly. Now my TA says that due to this HZ is more acidic then HX. Is this correct?
  2. jcsd
  3. Jul 18, 2012 #2
    Pretty much. Compare the acidity of HF, HCl, HBr and HI.
  4. Jul 19, 2012 #3
    Correct. Acidity is a related to the stability of the conjugate base. A larger anion is more stable on its own than a small one, so the equilibrium favors the dissociated H+ and Z-.
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