I crushed an aspirin tablet and got 341.5 mg which is more than a typical tablet weights (325 mg) why did this happen?

Question

We crushed 2 aspirin pills in lab and got the weight to be 683 mg. Divide that by 2 and each pill weighs about 341.5 mg. The pill weight on the bottle read 225 mg. Our percent error is, therefore, 5.08% but we have to explain why this happened?

 

Answer 1

The 225 mg on the bottle refers to the weight of the active ingredient, not the weight of the pill.  The pill will weigh more than 225 mg because of the inert and inactive ingredients used as binders, etc.  This is the likely explanation for what appears to be a rather large error in weighing.

Answer 2

There are several types of errors that can affect your results; the ones most relevant in this situation would be

1. random error--some random unidentifiable factor result in the fluctuations of results you observe.

2. instrument error--this is an observable error due to factors like instrument calibration etc.