When using the small pycnometer, the fixture is weighed together with the pycnometer.

• A. False
• B. Not Given
• C. True
• D. Not Applicable

Answer: (C)

When you determine density with a small pycnometer, you weigh the entire assembly—the pycnometer plus its fixture—together. This is because the fixture contributes to the overall mass that sits on the balance, and that total mass is what you use in the density calculations. If you left the fixture out of the tare mass, the mass difference you rely on to compute the liquid’s displacement would be incorrect, leading to an erroneous density result. Weighing the fixture with the pycnometer ensures the mass measurements accurately reflect what’s actually being weighed during the test, both empty and with the liquid in place.