Question #e1868

1 Answer
Sep 18, 2017

Answer:

Mix 468.75 mL 0.5% solution with 281.25 mL 0.1% solution.

Explanation:

Well, practically, if you are in a lab, the simplest thing to do would be to dilute the 50% solution! But, I assume that they really want you to simply mix the two given solutions together to make the math more interesting.

This is similar to a regular molarity or molality mixing problem. Two volumes of two concentrations equal one volume of another concentration, as long as the dimensions are the same. Two equations in two unknowns – no problem.

#X + Y = 750# This is the ratio of the two volumes. We can substitute one for the other to use in the next equation. #Y = 750 – X#

#0.5 xx X + 0.1 xx Y = 0.35 xx 750#
#0.5 xx X + 0.1 xx (750 - X) = 262.5# ; #0.5 xx X – 0.1 xx X + 75 = 262.5#

#0.4 xx X = 187.5# ; # X = 468.75# ; #Y = 750 – 468.75 = 281.25#

CHECK:
#0.5 xx X + 0.1 xx Y = 0.35 xx 750# ; #0.5 xx 468.75 + 0.1 xx 281.25 = 262.5#
#234.373 + 28.125 = 262.5# ; #262.5 = 262.5# CORRECT!