How to Convert Mole Fractions to Mass Percentages

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Converting mole fractions to mass isn't nearly as complicated as you might assume it's going to be. Convert mole fractions to mass with help from a research scientist and one of the world's leading experts on star formation in this free video clip.

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Video Transcript

Hello, my name is Harold Yorke, I'm a research scientist in Pasadena, California, and I'm going to explain how to convert from mole fractions into mass percentages. First let me define the term mole, one mole of a substance is this number of atoms or if it's a molecule, this number of molecules, that's a very big number. This is 6022 and then I have another 20 zeros. So I've rewritten that number 1 mole in scientific notation, 6.022 times 10 to the 23, it's a very large number. So suppose we're given the mole fractions of several components in a substance, green, blue, and red, I'm gonna note them green, blue and red. I need to know how many grams per mole substance green has. If it's an atom I would look it up in a table. For instance if it were carbon that number would be 12, if it were oxygen that number would be 16. Similarly for substance blue I look up the number and for substance red I look up the number, what is the grams per mole and that's given in a periodic table. I multiply now my mole percentage by this grams per mole and I get a number x, y, and z for substance green, blue, and red. Now the sum of x,y, and z in general will not be 100. So to make it into mass percentages they have to add up to be 100 and the way I do this is I add the number x, y, and z. So for the green substance the mass percentage is x divided by the sum of x,y, and z and then multiplied by 100 so that we have it in a percentage and similarly for the blue substance and the red substance I would work out, I would have to do the math and that's how to convert from molar fractions to mass fractions. Thank you for watching.


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