Question #745c2

1 Answer
Mar 9, 2017

Answer:

#1.0 * 10^(-4)"g NaCl"#

Explanation:

The thing to remember about concentrations expressed in parts per million is that they are calculated by looking at the number of parts of solute present for every #10^6# parts of solution.

In other words, you're looking for the number of grams of solute present in #10^6# grams of solution. This value will get you the solution's concentration in parts per million.

A #"1 ppm"# solution will thus contain #"1 g"# of solute for every #10^6# #"g"# of solution. Similarly, a #"100.0 ppm"# solution will contain #"100.0 g"# of solute for every #10^6# #"g"# of solution.

Now, you know that your solution must have a concentration of #100.0# ppm and that the mass of the solution is equal to #"1.0 g"#.

Your goal here will be to use the solution's parts per million concentration as a conversion factor to calculate the number of grams of sodium chloride, your solute, needed to make this solution.

#1.0 color(red)(cancel(color(black)("g solution"))) * overbrace("100.0 g NaCl"/(10^6color(red)(cancel(color(black)("g solution")))))^(color(blue)("= 100.0 ppm NaCl solution")) = color(darkgreen)(ul(color(black)(1.0 * 10^(-4)color(white)(.)"g NaCl")))#

The answer is rounded to two sig figs, the number of sig figs you have for the mass of the solution.