Which instrument is commonly used to measure the mass of atoms?

• A. Mass spectrometer
• B. Microscope
• C. Voltmeter
• D. Calorimeter

Answer: (A)

Verified step by step guidance

1. Understand that the question asks for an instrument used to measure the mass of atoms, which requires precise measurement at the atomic or molecular level.
2. Recall that a microscope is used to visualize small objects but does not measure mass, so it is not suitable for measuring atomic mass.
3. Recognize that a voltmeter measures electrical potential difference (voltage), which is unrelated to mass measurement.
4. Know that a calorimeter measures heat changes in chemical reactions, not mass.
5. Identify that a mass spectrometer is the instrument designed to measure the mass-to-charge ratio of ions, allowing determination of atomic and molecular masses.