PS5.8 a asks you to determine the molality. This part of the problem is pretty
straight forward. Part b is the challenging part of this problem. I will not
tell you exactly how to do part b, but here is a hint.
Density of a solution is defined as the grams of the solution/volume of the
solution. What concentration term that we discussed in class contains grams
of solution? What concentration term that we discussed in class contains volume
of solution? OK now can you arrange those two concentration terms to obtain
the density of the solution?
Hope this helps.