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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: esteebo on May 20, 2019, 02:57:25 PM

Title: Solubility Calculations
Post by: esteebo on May 20, 2019, 02:57:25 PM

I am a physics student, conducting an experiment wherein I want to mix some noble gases into solvents like C3F8 and C3FI, and I wanted to calculate their solubility beforehand (I will be working with parts per million, so I don't think I will reach that upper limit, but I still want it). I tried using Henry's Law, but as I was working through the calculations to get Henry's Law (everything I found had it for solutions using water at around room temperature), I noticed that it is only valid when using solvents around the same density as water. Flourocarbons are not close enough to use that. Are the other methods or equations that would work to calculate these solubility values?

Title: Re: Solubility Calculations
Post by: Borek on May 21, 2019, 03:11:43 AM

I am not sure I understand what you mean - Henry's law states that the concentration of dissolved gas is directly proportional to the partial pressure of the gas above solvent. As far as I am aware it: a. doesn't put any limit on the solubility, b. doesn't provide any way to calculate the proportionality constant (other than from experimental data).

I feel like you are talking about something else.

Title: Re: Solubility Calculations
Post by: esteebo on May 21, 2019, 08:22:53 AM

I had tried to calculate the constant using K=p/c, where p is the partial pressure of the solute, and c=bq/(1+bM), where q is the density of the solvent, b is the molality, and M is the molar mass of the solute. I am trying to find where I read it, but I did read somewhere that Henry's Law is only valid for dilute solutions where bM is far less than one, and the q value is close to that of water, neither of which is the case for dissolving Xenon or Argon into fluorocarbon.

Title: Re: Solubility Calculations
Post by: Enthalpy on May 22, 2019, 03:29:48 AM

Is that formula some magic means to predict a solubility, or rather a tautology? Something like "the amount is the amount". A formula that tells K once you have measured the solubility.

I find hard to believe that a formula with few generic terms like the molar mass could predict a solubility. How would it distinguish NH₃ in water from Ne?