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Posted by on Friday, March 4, 2011 at 7:26pm.

how do I prepare 50% and 70% ethanol from 95% ethanol?

  • chemistry - , Friday, March 4, 2011 at 10:05pm

    I assume the 50% and 70% are v/v. If so, then, 95% ethanol means you have 95 mL ethanol in a total volume of 100 mL (which doesn't necessarily mean the volume of water is 5.0 mL).To get 50 mL ethanol (from the 95% stuff) you need (50/95)*100 = 52.63 mL. (You can see that 52.63 mL (of 95% stuff) x 0.95 = 50 mL of PURE ethanol. Then add water to 100 mL total volume. For 70%, you need (70/95(*100 = approximately 75 mL.

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