Question #a4c01

1 Answer
May 5, 2017

Answer:

#1.7 * 10^3"ppm"#

Explanation:

The thing to remember about a mixture's concentration in parts per million, or ppm, is that it is supposed to tell you the number of parts of a given component of the mixture present for every

#10^6 = 1,000,000#

parts of mixture. In your case, you know that the sample has a total mass of #"70 g"#. This sample is said to contain #"0.119 g"# of iron.

Your goal here is to figure out how many grams of iron you would get for #10^6# #"g"# of sample by using its known composition.

#10^6 color(red)(cancel(color(black)("g sample"))) * "0.119 g Fe"/(70color(red)(cancel(color(black)("g sample")))) = 1.7 * 10^3# #"g Fe"#

This means that the sample's concentration in parts per million is equal to

#color(darkgreen)(ul(color(black)("concentration Fe" = 1.7 * 10^3color(white)(.)"ppm")))#

I'll leave the answer rounded to two sig figs, but keep in mind that you only have one significant figure for the mass of the sample.