The weight of the purified caffeine is often much lower than the weight of the crude caffeine. Explain why the percent recovery is frequently low?

see explanation

Explanation:

When caffeine is purified, the impurities are removed,  these impurities are responsible for the greater mass of pure caffeine compared to the mass of the pure sample.

The percent recovery of caffeine is frequently low because some caffeine is often left behind in the solvent during the process of recrystallization.

Secondly, since caffeine is a sublime substance, some caffeine may be lost o sublimation leading to a low percent recovery of pure caffeine.

the electron configuration that you gave me has 16 electrons ergo it has 16 protons ergo it is the element sulfur.

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.