Why is solubility of HBr Less Than HCl ?

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The discussion centers on the solubility and concentration differences between HBr and HCl in water. HBr has a maximum concentration of 8.9 moles/L, which is lower than HCl's 12 moles/L, despite HBr's more negative enthalpy of formation and hydration values. The vapor pressures indicate that HBr has a lower vapor pressure (4.5 mmHg) compared to HCl (15 mmHg) at their respective concentrations. The acid strength, as indicated by pH values, also shows HBr is stronger than HCl. The discussion suggests that the size of the ions may play a significant role in solubility, as the free energy values imply HBr should have a higher maximum concentration. Overall, the analysis indicates that while thermodynamic values favor HBr, practical solubility is affected by ionic size and other factors.
morrobay
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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 said:
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
 
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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