Rubidium has two naturally occurring isotopes, rubidium-85 (atomic mass $=84.9118$ amu; abundance $=72.15 \%$ ) and rubidium-87 (atomic mass = 86.9092 amu; abundance = 27.85$\%$ ). Calculate the atomic weight of rubidium.
Added by Cody H.
Step 1
The contribution of an isotope to the atomic weight is calculated by multiplying its atomic mass by its abundance. For rubidium-85: Contribution of rubidium-85 = (atomic mass of rubidium-85) x (abundance of rubidium-85) = 84.9118 amu x 0.7215 For Show more…
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Rubidium has two naturally occurring isotopes: Rb-85 with a mass of 84.9118 amu and a natural abundance of 72.17%, and Rb-87 with a mass of 86.9092 amu and a natural abundance of 27.83%. Calculate the atomic mass of rubidium.
Ma Ednelyn L.
The atomic weight of rubidium is $85.4678$ amu. The two naturally occurring isotopes of rubidium have the following masses: ${ }^{85} \mathrm{Rb}, 84.9118$ amu; ${ }^{87} \mathrm{Rb}, 86.9092$ amu. Calculate the percent of ${ }^{85} \mathrm{Rb}$ in naturally occurring rubidium.
Two isotopes of rubidium occur naturally, with $^{85}_{37} \mathrm{Rb}$ at $72.17 \%$ $(84.91 \text { amu })$ and $^{87}_{37} \mathrm{Rb}$ at $27.83 \%(86.91 \mathrm{amu}) .$ Calculate the atomic mass for rubidium using the weighted average mass method.
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