SOLUTION: A flask contains 500 ml of an 80% alcohol solution in water. How much of this solution must be drawn off and replaced by water to obtain a solution having a concentration of 25% a

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Question 1186856: A flask contains 500 ml of an 80% alcohol solution in water. How much of this solution must be
drawn off and replaced by water to obtain a solution having a concentration of 25% alcohol?
Answer by josgarithmetic(39621) About Me  (Show Source):
You can put this solution on YOUR website!
Begin with 500 ml and finish with 500 ml. volume

alcohol%2Fsolution=targetfraction

v, amount to remove and replace
%280.8%2A500-0.8v%29%2F500=0.25----------because 25% is the desired finished concentration.

0.8%2A500-0.8v=0.25%2A500
0.8%2A500-0.25%2A500=0.8v
v=%280.8%2A500-0.25%2A500%29%2F0.8---------------compute this.