SOLUTION: I need to mix a cleaning solution that would spray out of a bottle and contain 70% rubbing alcohol to clean lab surfaces. To save cost, it makes sense to add water to some amount o

Question 980554: I need to mix a cleaning solution that would spray out of a bottle and contain 70% rubbing alcohol to clean lab surfaces. To save cost, it makes sense to add water to some amount of alcohol yet maintain the 70% level. Average spray bottles likely hold about 25 fl ounces or what about 800 ml? What should my solution look like? Thank you. Leann
Found 2 solutions by ankor@dixie-net.com, josgarithmetic:
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
add water to some amount of alcohol yet maintain the 70% level.
Average spray bottles likely hold about 25 fl ounces or what about 800 ml?
What should my solution look like?
:
let x = amt of alcohol to be removed and amt of water to be added
Lets use an amt of alcohol to be 25 oz
25 - x = .7(25)
25 - x = 17.5
-x = 17.5 - 25
-x = -7.5
x = 7.5 oz of alcohol removed and 7.5 oz of water added maintaining a 25 oz bottle
Answer by josgarithmetic(39617) (Show Source): You can put this solution on YOUR website!
What are your materials? If you add some amount of water to 70% alcohol, then you will obtain a concentration of alcohol LESS THAN 70%.

If you are starting with 100% alcohol and want to add some water to prepare 25 fluid ounces of 70% alcohol, then ...

v, volume of the "pure" alcohol of 100%;
25-v, volume of the water to add;

Find v, and then find 25-v.
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