# Conversion of a value between g/gmol and lb/lbmol

I am doing some air emissions calculations and I really just have a bad feeling about my results. By definition, molecular weights are given in $\pu{g/gmol}$. For the substance I have, I was told by a technical contact at Citgo that this material has a molecular weight of $\pu{140 g/mol}$ (which should be $\pu{g/gmol}$). Whenever I convert this $\pu{lb/lbmol}$ (which is required for this particular equation), I'm getting a value of $\pu{0.3086 lb/lbmol}$. There are 453 grams in a pound. Is it not correct to divide 140 grams by 453 grams to get the total number of pounds?

My final result for annual emissions is pretty low.

A gram-mole ($\pu{gmol}$),often just called a mole ($\pu{mol}$), is the amount of a material whose mass in grams equal to the numerical value of the atomic or formula mass. For example, a gram-mole of water has a mass of 18.017 grams, this number being the formula mass for water.

A pound-mole ($\pu{lbmol}$) is the amount of a substance whose mass in pounds-mass equals the atomic or formula mass. For water, one pound mole has a mass of $18.017$ lb-mass.

The pound-mole is bigger than the gram-mole by the same factor as a pound is bigger than a gram - so pounds per pound-mole equals grams per gram-mole. You do not divide by anything.

If the amount of weight you are measuring it in is pounds then use pound moles if the amount your measuring in is grams use gram moles.

140g/g-mol = 140lb/lb-mol

that explanation is confusing to people the simplest way i have seen it explained is that 453.592gmol = 1 lbm-mol

so if you are given the weight of a substance say you have 1000lbm of hydrogen and you want to know the amount of moles.

simply do 1000lbm * lbmol/2lbm = (500lbmol)*453.592gmol/1lbm-mol = 226,796 gmol. If you want to convert the other way do the exact opposite.

btw lbm is lbm just means pounds weight not lbf pounds force.

https://www.calculand.com/unit-converter/?gruppe=Molar+Mass&einheit=Pound+per+pound-mole+%5Blb%2Flbmol%5D

1 lb / lb-mol is exactly 1 g / mol, because 1 lb-mol is 453,59 mol, which is the same ratio that there is between lb and g. The link above is a very useful converter.