MCAT General Chemistry Question 9: Answer and Explanation
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Question: 9
9. Which of the following best explains the inability to measure position and momentum exactly and simultaneously according to the Heisenberg uncertainty principle?
- A. Imprecision in the definition of the meter and kilogram
- B. Limits on accuracy of existing scientific instruments
- C. Error in one variable is increased by attempts to measure the other
- D. Discrepancies between the masses of nuclei and of their component particles
Correct Answer: C
Explanation:
The limitations placed by the Heisenberg uncertainty principle are caused by limitations inherent in the measuring process: if a particle is moving, it has momentum, but trying to measure that momentum necessarily creates uncertainty in the position. Even if we had an exact definition of the meter, as in choice (A), or perfect measuring devices, as in choice (B), we still wouldn't be able to measure position and momentum simultaneously and exactly.