Ch_2-2_Average_Mass_Isotopes_for_PDF

# Ch_2-2_Average_Mass_Isotopes_for_PDF - CALCULATING AVERAGES...

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CALCULATING AVERAGES METHOD 1 Test scores: 90, 60, 60, 60, and 80 80 3 60 90 350 Test Average 70 55 x + + = == METHOD 2 80 3 60 90 1 3 1 Test Average 80 60 90 16 36 18 70 5 5 x + + = = + + =++= () () ( ) 0.2 80 0.6 60 0.2 90 16 36 18 70 or + + = How to do calculation ()() ( ) 20% 80 60% 60 20% 90 or =++ How data presented

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Example 1 : Find the average mass. The mass spectrum of an element shows the following percent abundance and corresponding masses: Æ 0.7899 x 23.985 u = 18.946 u Æ 0.1000 x 24.986 u = 2.499 u Æ 0.1101 x 25.982 u = 2.861 u 78.99% 23.985 u 10.00% 24.986 u 11.01% 25.982 u + 24.31 u Mg Found by looking at Periodic Table Note, most abundant isotope is about 24 u and answer is closest to 24 u (not 25 u or 26 u which are the approximate masses for the less abundant isotope).
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Ch_2-2_Average_Mass_Isotopes_for_PDF - CALCULATING AVERAGES...

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