In a high school science class, Riley was given 50 milliliters of water and 50 milliliters of ethanol. His task was to mix them together and then run an experiment on the mixture.
When the teacher came to check on him, however, Riley's mixture only contained 94 milliliters. The teacher accused him of drinking some of the mixture in an attempt to get intoxicated and immediately sent him to the principal. Riley swore that he did NOT drink the mixture and he didn't lose any of the liquids by any means.
What happened to the other 6 milliliters and how could Riley prove his innocence?
If the teacher had performed the experiment themselves, they wouldn't have accused the student in the first place. Unlike mass, volume isn't an additive property of substances. So while 50 grams of ethanol plus 50 grams of water will indeed equal 100 grams of the water/ethanol mixture, the same is not true for volume due to the way that water molecules and ethanol molecules interact with each other.
As far as how the student could prove this to the teacher, they could try repeated distillation of the ethanol/water mixture, although this is complicated by the fact that ethanol and water form a constant boiling azeotrope of about 95% ethanol. Nonetheless, if the student is careful to trap and recondense the vapors produced by distilling the mixture, they should be able to show the teacher that the combined volume of the water-rich and ethanol-rich fractions increases as the two fractions separately approach 100% purity.
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Posted by H M
on 2022-04-16 18:18:56 |
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