Why is solubility of HBr Less Than HCl ?

  1. The maximum concentration of dissolved HBr , 8.9 moles/L is less than HCl 12 moles/L
    The values from table below from various sources suggest that HBr should be more soluble at STP in 1 liter water ?
    ...............................................HBr....................................HCl
    enthalpy of formation.................-53kJ.mole >>>>>>>>>>>>>>>-96kJ/mole
    enthalpy of hydration/dissociation -64kJ/mole<<<<<<<<<<<<<<<-60kJ/mole
    vapor pressure........................... 16mmHg<<<<<<<<<<<<<<<<<28mmHg
    Ka ...........................................9>>>>>>>>>>>>>>>>>>>>>>7
    ΔG=-RTlnKeq(Ka)........................<<<<<<<<<<<<<<<<<<<<<<<<
    Acid strength..............................>>>>>>>>>>>>>>>>>>>>>>>>
    pH...........................................-.95>>>>>>>>>>>>>>>>>>>>>-1.08
    dissolved mass..........................712g>>>>>>>>>>>>>>>>>>>>>>432g
     
  2. jcsd
  3. Correction : Vapor pressures at above concentrations HCl , 12 m/l = 15 mm Hg
    HBr, 8.9 m/l = 4.5 mm Hg.
    Dissolved mass is for general information only
    Just based on a more negative free energy alone should indicate a higher maximum concentration for HBr
     
  4. Borek

    Staff: Mentor

    I have a gut feeling we can't ignore size of the ion - while the molar values are different, there is only so much of a substance that fits given volume.

    Or at least that would be the starting point for my analysis. Doesn't have to yield any explanation.
     
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