1. A student was tasked to repeat this experiment three times byexactly the same

Question

1. A student was tasked to repeat this experiment three times byexactly the same procedure in
order to estimate the experimental uncertainty in the determinationof optical rotation using
this experimental procedure and the same equipment. He obtained[a]D values of +138.8°,
+141.4° and +139.9°. As his final value, he reported+139.9°± 1.5° because, as he
explained, all of his measurements were within 1.5° of themedian value. Is this correct
procedure? What should he have reported instead? Show yourwork.
2. A chemist wants to resolve a particular amine, but she has notartaric acid on hand. Which
of the following acids would not be possible replacements for thetartaric acid used in this
experiment: malic, citric, mandelic, lactic, glycolic or glycericacids? Why?
3. In this experiment, the maximum isolatable yield of any oneenantiomer is 50%, because the
amine is racemic. If the amine had been already partly resolved to65% optical purity, what
would be the maximum yield of optically pure amine in thisexperiment. Explain.

Explanation / Answer

a) The standard deviation always has only one significant figure.Thus it should be 140±2

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