SOLUTION: How much water should be added to 12 mL of 8​% alcohol solution to reduce the concentration to 6​%?

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Question 1208155: How much water should be added to 12 mL of 8​% alcohol solution to reduce the concentration to 6​%?
Found 2 solutions by ikleyn, timofer:
Answer by ikleyn(52776) About Me  (Show Source):
You can put this solution on YOUR website!
.
How much water should be added to 12 mL of 8​% alcohol solution to reduce the concentration to 6​%?
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Your original solution contains  0.08 * 12 = 0.96 mL  of pure alcohol.


You want to have the new total volume  V  such that  0.96 mL  of pure alcohol
make the concentration  0.06.


Write an equation saying that  0.06  of  V  is  0.96

    0.06*V = 0.96.


Solve it and find  V

    V = 0.96/0.06 = 16 mL.


So, the original volume is/was 12 mL; new volume should be 16 mL.

Hence,  16 - 12 = 4 mL of water should be added.


ANSWER.  4 mL of water should be added.


CHECK.    0.96%2F16 = 0.06,  correct.

Solved.



Answer by timofer(104) About Me  (Show Source):
You can put this solution on YOUR website!
volume and concentration before and volume and concentration after
must give the same amount of dissolved material.


12%2A8=x%2A6
and then
x=%2812%2A8%29%2F6
x=16mL the final volume; but how much water to add to get there, 16-12=4.
Add 4 mL.