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equilibrium so that some O2(g) is consumed (tending to relieve the stress) as
more U3O8(s) is produced. One point is earned for
a correct explanation. © 2007 The College Board. All rights reserved.
Visit apcentral.collegeboard.com (for AP professionals) and www.collegeboard.com/apstudents (for students and parents). AP® CHEMISTRY
2007 SCORING GUIDELINES (Form B)
Answer the following problems about gases.
(a) The average atomic mass of naturally occurring neon is 20.18 amu. There are two common isotopes of
naturally occurring neon as indicated in the table below.
Ne-22 Mass (amu)
21.99 (i) Using the information above, calculate the percent abundance of each isotope.
Let x represent the natural abundance of Ne-20.
19.99 x + 21.99(1− x)
19.99 x + 21.99 − 21.99 x
19.99 x − 21.99 x
⇒ percent abundances are: =
20.18 − 21.99
0.905 One point is earned for the correct answer. Ne-20 = 90.5%
Ne-22 = 9.5% (ii) Calculat...
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- Spring '09