Which is a stronger acid HCl or HI Strengths of Acids

Which is a stronger acid HCl or HI

 

The question is which acid is stronger. Is it HCL or HI.  According to Arrhenius theory an acid is a substance that increases the concentration of the hydrogen ions in aqueous solutions. The ability of substances to ionize and produce hydronium ions varies.

 

The bond strength is an indication of the strength of an acid. The strength of the bond between hydrogen and the Anion. The second is the stability of the negative ion or anion or the conugate base that is formed. And the third reason is the nature of the solvent used, in this case, the solvent is water.

The reasons can be rationalized using the following points in order to explain which acid is a stronger acid HCl or HI.

  • An acid is a substance that can produce a hydronium ion in solution according to Arrhenius theory. Bronsted Lowry theory states that an acid is a proton donor.
  • The stronger an acid it is easier to release a proton in solution.
  • Now comparing the bond strength between HI and HCl we find that the HI bond is weaker as Iodine is much larger than chlorine and cannot form an effective overlap between the s orbital of Hydrogen  and the p orbital of Iodine, so relatively the H-Cl bond is stronger due to the better overlap of the sigma bonds.
  • Since the H-Cl bond is stronger bond it is a weaker acid, therefore it is more difficult to break the H-Cl bond as compared to H-I.
  • It would be easier to release a Hydrogen ion from HI than from HCl.
  • This logic may be applied to similar oxy-acids too.

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