Question

A chemistry student performs an extraction of caffeine from coffee grounds using 2.316 g. They tare the watch glass (recorded the empty watch glass weight) before they add their caffeine to it after distillation. They find their crude product has a mass of 186 mg. What is the mass of caffeine extracted from the coffee grounds?

Answer 1

The mass of caffeine extracted is 186 mg, which is the mass of the crude product recorded after taring the watch glass.

Step-by-step explanation:

The mass of caffeine extracted from the coffee grounds is calculated by subtracting the weight of the empty watch glass from the total weight of the watch glass with the crude caffeine product. After distillation, if the watch glass with the caffeine has a mass of 186 mg, and assuming the watch glass itself was tared (weight recorded and then reset to zero), then all of this mass is attributable to the caffeine. Therefore, the mass of caffeine extracted is 186 mg.