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Why is solubility of HBr Less Than HCl ?

by morrobay
Tags: solubility
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morrobay
#1
Mar15-13, 02:12 AM
P: 382
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
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morrobay
#2
Mar15-13, 08:19 PM
P: 382
Quote Quote by morrobay View Post
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
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
Borek
#3
Mar16-13, 04:06 AM
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P: 23,733
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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