Do impurities raise or lower the property of an organic compound such as lower or raise an equivalent weight?
1 answer
I guess it depends upon the property. With respect to melting point, you know an impurity causes the m.p. to be lower AND to be less sharp. With regard to equivalent weight, I never thought about it. No, it can't change the equivalent weight BUT it can change the APPARENT equivalent weight. So if we had benzoic acid, with an equivalent weight of 122.1 and it was contaminated with something unreactive (such as sand) then we might weigh our sample and it might consist of 122.1 g composed of 61.05 g sand and 61.05 g benzoic acid. When we determined the equivalent weight by titrating with a standard base, we would use Lbase x Normality base = equivalents base. That would equal the number of equivalents of our fake benzoic acid. Equivalents = g/equivalent weight. g is the same 122.1 as always, but since we had only half the benzoic acid in the sample then the base will be half what it should be, the equivalent weight will be double what it should be. But suppose the benzoic acid sample was contaminated with another acid of different equivalent weight. It might go down or up. I hope this is what you were looking for. In short, the apparent equivalent weight can change.