Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: OrganicH2O on August 31, 2020, 12:41:14 PM
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If a solution is given as a percent, with no actual units given, what are the default units? I understand that percent could mean several different things, such as as Mass/Mass, Volume/Volume, or Mass/Volume. If Mass/Volume is used, the units seem arbitrary.
I see percent given on many different real world items, and the units are rarely provided.
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The percent is a dimensionless quantity.
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I understand that it's typically a dimensionless quantity, but if the units are mass/volume, is that really dimensionless?
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if the units are mass/volume, is that really dimensionless?
m/v% are faulty by design. This is just a way of describing the solution preparation procedure, not a real percentage.
If you want to be nitpicky you can assume their units to be g/mL% (whatever that means).
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This is a difficult question to answer, although there is a decent discussion in a very old quantitative analysis textbook by Pierce, Haenish, and Sawyer. Context counts for quite a bit, because various sub-disciplines have conventions that are probably not known by those in other sub-disciplines.
IMO the author should always specify what is being measured and whether an initial or a final volume is meant. If the author does not, then the experimenter must make an educated guess. The substances were two liquids, I would assume volume to final volume of solution. If the substances were a solid and a liquid, I would assume mass to final volume of solution. You might want to ask yourself whether other assumptions would lead to small or large differences in strength of a solution.