homework help 834

Ppm stands for “parts per million”.

In other words, “How many grams are in one million grams of the sample?”

In the same way, mass percent is the number of grams in 100 g of the sample.

For example, ##”73.2 ppm” = “73.2 g”/(10^6 “g”)## of sample.

We want to know the mass of the component in ##100color(white)(l) “g”##, so we divide both numerator and denominator by ##10^4##.

##”% by mass” = (“73.2 g” -: 10^4)/(10^6 “g” -: 10^4) = “0.007 32 g”/(100color(white)(l) “g”) = “0.007 32 %”## (m/m)