Henry's Law - Hcc vs. Hyx Method (prob. a basic question)

[kg3]

I'm going a little crazy...I can't figure out where my factor of 10 difference is coming from when I use mole fraction vs. concentration methods for Henry's law. I'm a little rusty on this (haven't done it much since college) so any help would be appreciated.

Assume 20degC and 101.325 kPa; Hcc=0.9642 for CCl4
have 30,000 ppm in vapor phase
MW of CCl4=153.82:
converted ppm to mg/m3:
mg/m3 = 30,000(153.82*101.325)/(8.3144*293)
30,000ppm = 191,934 mg/m3
Then using Hcc.... liq=191,934/0.9642=199,015 mg/m3
or 199mg/L
199mg/L = 199ppm in liquid phase

Mole Fraction Method:
The Hyx for 20degC is 1330
y(molefraction) = 30,000ppm/1E6= 0.03
x(molefraction)=0.03/1330=2.25x10-5
multiplying by 1E6.....liquid CCl4 is ~23 ppm

I orginally did the calc using Hyx; but found old numbers calculated with concentrations....and mine are 10x off the original ones. I found an EPA conversion tool on-line and it converted Hcc=0.9642 at 20C to Hyx=1300.

HELP!! What am I missing? Thanks in advance.

 

[rbcoulter]

The problem is that you forgot to account for the fact that the liquid phase is almost entirely water. To make it easy to understand, calculate based on some basis, for example, one gram-mole of liquid. Calculate the volume of water using mw of 18. Calculate mg of carbon tet using your calculation and mw of carbon tet. I believe your results will match then.

 

[kg3]

Thank you.....that was it. I knew I was making a stupid mistake somewhere.