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  • Conversion of molar unit to mmol/mol?

    Greetings all, gas chemistry, let alone basic chemistry and unit conversions was a loooong time ago for me and I'm trying to wrap my head around using data from two different publications, but their data are reported in different units.

    On the one hand, a publication reports carbon dioxide (CO2) as mmol/mol and another publication reports gases in molar quanties as a percent (%) and as parts per million (ppm) and parts per billion (ppb). I've looked at other postings on this site for conversions between ppm and molar percentages and I think I understand this, but I could be stretching it.

    So, let's that a publication posts carbon dioxide data for sites 1A, 2A, and 3A as mmol/mol quantities. 1A = 900, 2A = 600 and 3A = 500.

    What would the corresponding measurements for 1A be as a %, as ppm, and as ppb. If you could show your calculation then I could apply the method for 2A and 3A, as well.

    Many, many thanks in advance!

  • #2
    Re: Conversion of molar unit to mmol/mol?

    Originally posted by Unregistered View Post
    Greetings all, gas chemistry, let alone basic chemistry and unit conversions was a loooong time ago for me and I'm trying to wrap my head around using data from two different publications, but their data are reported in different units.

    On the one hand, a publication reports carbon dioxide (CO2) as mmol/mol and another publication reports gases in molar quanties as a percent (%) and as parts per million (ppm) and parts per billion (ppb). I've looked at other postings on this site for conversions between ppm and molar percentages and I think I understand this, but I could be stretching it.

    So, let's that a publication posts carbon dioxide data for sites 1A, 2A, and 3A as mmol/mol quantities. 1A = 900, 2A = 600 and 3A = 500.

    What would the corresponding measurements for 1A be as a %, as ppm, and as ppb. If you could show your calculation then I could apply the method for 2A and 3A, as well.

    Many, many thanks in advance!
    It is basically prefix shuffling, and the moles in numerator and denominator make it dimensionless 900 mmol/mol = 0.9 mol/mol, or a decimal fraction 0.9 (parts per part) concentration of CO2. Percent is parts per hundred so 90% CO2 (I suppose you could say 90 cmol/mol).

    Parts per million is better expressed as µmol/mol. If the mole fraction is 0.9, multiply by 1 million for parts per million instead of parts per part. Get 900 000 µmol/mol

    Parts per billion is nmol/mol, multiply decimal fraction 0.9 by one billion
    900 000 000 nmol/mol

    Are you sure the data is in mmol/mol (millimoles per mole) and not µmol/mol (micromoles per mole)? These are very high levels of CO2 (fatal to humans at these levels) from 50% to 90% of the mixture.

    Comment


    • #3
      Re: Conversion of molar unit to mmol/mol?

      Ha! JohnS, you're "right on the money" about those concentrations being lethal! Those data are from volcanic emissions and, unfortunately, they inevitably did kill the original researcher over time due to exposure.

      I'm a geochemist (previously, more in the realm of aqueous geochemistry) and now working on gas geochemistry and with a whole new set of units to deal with. I had scratched my head a little more after posting this thread and after considering the units, thought that it might just be a matter of decimal movement. Thanks goodness I wasn't too far off track.

      Many, many thanks for the thorough reply!

      Comment


      • #4
        Re: Conversion of molar unit to mmol/mol?

        Originally posted by Unregistered View Post
        Ha! JohnS, you're "right on the money" about those concentrations being lethal! Those data are from volcanic emissions and, unfortunately, they inevitably did kill the original researcher over time due to exposure.

        I'm a geochemist (previously, more in the realm of aqueous geochemistry) and now working on gas geochemistry and with a whole new set of units to deal with. I had scratched my head a little more after posting this thread and after considering the units, thought that it might just be a matter of decimal movement. Thanks goodness I wasn't too far off track.

        Many, many thanks for the thorough reply!
        Hi,

        I can relate to the struggle in converting gas chemistry units. I am a geologist, functioning as a geochemist in an operating geothermal field, you can imagine the STRUGGLE.

        In CO2, we use the units mmole/100mol H2O, but one of the labs gave us concentration in ppm by weight. Can you please help me convert the CO2 content from ppm to mmole/100mol H2O. They gave the gas/steam ratio (in ppm by Weight) and total weight of condensate (in grams) as well as the amount of water vapor (also in ppm by weight).

        Comment


        • #5
          Re: Conversion of molar unit to mmol/mol?

          Originally posted by Unregistered View Post
          Hi,

          I can relate to the struggle in converting gas chemistry units. I am a geologist, functioning as a geochemist in an operating geothermal field, you can imagine the STRUGGLE.

          In CO2, we use the units mmole/100mol H2O, but one of the labs gave us concentration in ppm by weight. Can you please help me convert the CO2 content from ppm to mmole/100mol H2O. They gave the gas/steam ratio (in ppm by Weight) and total weight of condensate (in grams) as well as the amount of water vapor (also in ppm by weight).
          ppm (w/w) may be expressed with units as mg/kg. The molar mass, using rounded units, is 44 g/mol for CO2, 18 g/mol for water.

          1 mmol (CO2)/100 mol (H2O) may be expressed as 44 mg/1.8 kg, or 24.44 mg/kg, or ppm (w/w).

          Convert numerator and denominator as follows:

          mg/kg x 1 mol/44 g (CO2) x 1.8 kg/100 mol (H2O)

          Comment


          • #6
            As it would be in the case of mmol gas / Kg steam to mmol / 100 moles of water steamr?

            Comment


            • #7
              You convert molarity to millimolarity by multiplying by 1,000. For example, a 1 mol (molar, also written as M) solution has a concentration of 1 mole per liter. This is equivalent to a 1,000 Mmol (millimolar, also sometimes written as mM) solution, which is one that contains 1,000 Mmol per liter.

              Comment


              • #8
                Originally posted by Unregistered View Post
                Greetings all, gas chemistry, let alone basic chemistry and unit conversions was a loooong time ago for me and I'm trying to wrap my head around using data from two different publications, but their data are reported in different units.

                On the one hand, a publication reports carbon dioxide (CO2) as mmol/mol and another publication reports gases in molar quanties as a percent (%) and as parts per million (ppm) and parts per billion (ppb). I've looked at other postings on this site for conversions between ppm and molar percentages and I think I understand this, but I could be stretching it.

                So, let's that a publication posts carbon dioxide data for sites 1A, 2A, and 3A as mmol/mol quantities. 1A = 900, 2A = 600 and 3A = 500.

                What would the corresponding measurements for 1A be as a %, as ppm, and as ppb. If you could show your calculation then I could apply the method for 2A and 3A, as well.

                Many, many thanks in advance!
                A mmol/mol is a part per thousand whereas a percent is a part per hundred. 10 mmol/mol = 1%.

                Comment


                • #9
                  Originally posted by Unregistered View Post
                  Greetings all, gas chemistry, let alone basic chemistry and unit conversions was a loooong time ago for me and I'm trying to wrap my head around using data from two different publications, but their data are reported in different units.

                  On the one hand, a publication reports carbon dioxide (CO2) as mmol/mol and another publication reports gases in molar quanties as a percent (%) and as parts per million (ppm) and parts per billion (ppb). I've looked at other postings on this site for conversions between ppm and molar percentages and I think I understand this, but I could be Speed Test Scrabble Word Finder Solitaire stretching it.

                  So, let's that a publication posts carbon dioxide data for sites 1A, 2A, and 3A as mmol/mol quantities. 1A = 900, 2A = 600 and 3A = 500.

                  What would the corresponding measurements for 1A be as a %, as ppm, and as ppb. If you could show your calculation then I could apply the method for 2A and 3A, as well.

                  Many, many thanks in advance!

                  As it would be in the case of mmol gas / Kg steam to mmol / 100 moles of water steamr?

                  Comment

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