SOLUTION: I need to make a 20% solution of alcohol. I have on hand 70% alcohol. What formula do I use to dilute the 70% into 20% using sterile H2O?

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Question 629163: I need to make a 20% solution of alcohol. I have on hand 70% alcohol. What formula do I use to dilute the 70% into 20% using sterile H2O?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

dilute the 70% alcohol solution into 20% alcohol solution usinghighlight%28x%29 sterile H2O

  water = water

 x + .30A = .80(A+x)

      .20x = .5A

         x = .5A/.2

         x = 2.5A     Add 2.5 times as much water as the amount of 70% solution used



For ex:  using 10L of 70% solution  ⇒  25+%2B+.30%2A10+=+.80%2A35+=+28