How do I convert purity percentage to grams? [closed]








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I'm trying to find out how many grams of a substance, in this case propylene glycol, are in a 5 litre container that is advertised as being 99.8% pure. Any help would be greatly appreciated.




I'll do the "full problem". 


First the volume of a liquid typical increases with a rise in temperature. Since no temperature was specified, one must be assumed. The 88th CRC Handbook of Chemistry and Physics gives 1.0361 g/cu cm at 20 °C. So to work the problem you must assume:


(1) The density of 99.8% propylene glycol is 1.0361 g/ml @ 20 °C  




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> Note: For a catalog the specification is typically given as "at least 99.8%" and if reagent grade then an analysis for the particular batch would be given for the "fresh" bottle. Being hygroscopic, it is quite possible to pick up water from the air once the bottle was opened.
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(2) The volume is given for 20 °C  

(3) Since the OP is buying $\pu{5 L}$, I find it hard to believe that the volume would be 10% off. So let's assume that the quoted volume is good to $\pu{\pm10 ml}$, which means that the OP can expect 5.00 L. 


Thus:


$$\pu{5.00 L}\cdot \pu{1.0361 kg/L} \cdot \pu{0.998}\text{ pure} = \pu{5.170139 kg} \ce{->[rounded]} \pu{5.17 kg}$$


So $\pu{5.17\pm 0.01 kg}$ would be my answer. 


 2

In Wikipedia, propylene glycol has a density $1.04$. So $5$ litre propylene glycol weighs $5200$ g, and contains $5200·0.998 = 5190$ g propylene glycol. 


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