Chemistry: Molecular Approach (4th Edition)

Published by Pearson
ISBN 10: 0134112830
ISBN 13: 978-0-13411-283-1

Chapter 2 - Exercises - Page 80: 79


\[\underline{\text{152 amu}}\]

Work Step by Step

Calculate the abundance of Eu-153 as follows: \[\begin{align} & \text{Abundance of Eu-}153=\frac{100\,\text{percent}}{100\,\text{percent}+88\,\text{percent}}\times 100\,\text{percent} \\ & =53.19\,\text{percent} \end{align}\] Calculate the abundance of Eu-151 as follows: \[\begin{align} & \text{Abundance of Eu-}151=\frac{88\,\text{percent}}{100\,\text{percent}+88\,\text{percent}}\times 100\,\text{percent} \\ & =46.81\,\text{percent} \end{align}\] Calculate the Eu-153 fraction as follows: \[\begin{align} & \text{Fraction isotope Eu-}153=\frac{53.19}{100} \\ & =0.5319 \end{align}\] Calculate the Eu-151 fraction as follows: \[\begin{align} & \text{Fraction isotope Eu-}151=\frac{46.81}{100} \\ & =0.4681 \end{align}\] Calculate the atomic mass of the element as follows: \[\begin{align} & \text{Atomic mass}=\left( \text{fraction of Eu-}153\times \text{mass of Eu-}153 \right)+ \\ & \left( \text{fraction of Eu-}151\times \text{mass of Eu-}151 \right) \\ & =\left( 0.5319\times 153\text{ amu} \right)+\left( 0.4681\times 151\text{ amu} \right) \\ & =81.38\text{ amu}+70.68\text{ amu} \\ & =152.06\text{ amu}\,\,\approx \,\,152\text{ amu}\, \end{align}\] The atomic mass of europium is \[\underline{\text{152 amu}}\].
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