235UF6 effuses faster than 238UF6 QUESTION: Consider a gas containing 0.7% 235UF6 and 99.3% 238UF6. If the gas is contained in chamber A, as illustrated below, and is allowed to escape through a pinhole into vacuum chamber B, the percentage of 235UF6 in the gas that initially emerges in chamber B will be… A. higher than 0.7%, B. lower than 0.7%, C. still 0.7% Consider a gas containing uranium hexafluoride. Suppose 0.7% of the molecules have the uranium-235 isotope and the remaining 99.3% contain the uranium-238 isotope, and the gas is contained in chamber A, as illustrated below. If the gas is allowed to escape through a pinhole into vacuum chamber B, the percentage of molecules with the uranium-235 isotope in the gas that initially emerges in chamber B will be… A. higher than 0.7%, B. lower than 0.7%, C. still 0.7% PAUSE At the same temperature, lighter molecules move faster… on average. This means that the molecules with the lighter isotope… uranium-235… will be able to go faster through the pinhole into the vacuum chamber. The gas that emerges in chamber B will initially be richer in uranium-235 than the the original gas. The correct answer is A. The movement of a gas into a vacuum chamber through a pinhole is called effusion. We say that the molecules with uranium-235 effuse faster Than molecules with uranium-238. CLICK PAUSE END RECORDING 235UF6 effuses faster than 238UF6

Video ID: 1-12-1 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08