why the recrystallization of the diels-alder product, 9,10-dihydroanthracene-9,10-dicarbo xylic anhydride, was only approximately 60%?
a - the product evaporated with the solvent during the recrystallization
c - the product is partially soluble in xylene
d - there was some lost by sublimation

answer by yourhope:

how do models compare to real-world objects?

d. most models represent a real-world object in a simpler way.

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chemical digestion occurs in the stomach were hcl and pepsin forms chyme, the mouth in which salivary amylase breaks down starch to form bolus, and the small intestine specifically the duodenum.

aquifers are bounded above and below by impermeable rock. the driving force of groundwater movement in confined aquifers is pressure, rather than gravity.