Rubidium is a soft, silvery-white metal that has two common isotopes, $^{85} R b$ $""^85 Rb$ and $^{87} R b$ $""^87 Rb$ . If the abundance of $^{85} R b$ $""^85 Rb$ is 80.2% and the abundance of $^{87} R b$ $""^87 Rb$ is 19.8%, what is the average atomic mass of rubidium,?

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Rubidium is a soft, silvery-white metal that has two common isotopes, $^{85} R b$ $""^85 Rb$ and $^{87} R b$ $""^87 Rb$ . If the abundance of $^{85} R b$ $""^85 Rb$ is 80.2% and the abundance of $^{87} R b$ $""^87 Rb$ is 19.8%, what is the average atomic mass of rubidium,?

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Answer 1 · 2016-02-09T09:07:35

The average atomic mass should be the WEIGHTED AVERAGE of the individual isotopes.

Explanation:

So, we take the weighted atomic mass of $^{87} R b$ $""^87Rb$ and $^{85} R b$ $""^85Rb$ .

$(85 \times 80.2 % + 87 \times 19.8 %) amu = 85.40$ $(85xx80.2% + 87xx19.8%)"amu" = 85.40$ $amu$ $"amu"$ . Check to see if this atomic mass is close to that listed on the Periodic Table, which of course considers ALL the isotopes,

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Rubidium is a soft, silvery-white metal that has two common isotopes, $^{85} R b$ $""^85 Rb$ and $^{87} R b$ $""^87 Rb$ . If the abundance of $^{85} R b$ $""^85 Rb$ is 80.2% and the abundance of $^{87} R b$ $""^87 Rb$ is 19.8%, what is the average atomic mass of rubidium,?

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Rubidium is a soft, silvery-white metal that has two common isotopes, 85Rb""^85 Rb and 87Rb""^87 Rb. If the abundance of 85Rb""^85 Rb is 80.2% and the abundance of 87Rb""^87 Rb is 19.8%, what is the average atomic mass of rubidium,?

1 Answer

Explanation:

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Rubidium is a soft, silvery-white metal that has two common isotopes, $^{85} R b$ $""^85 Rb$ and $^{87} R b$ $""^87 Rb$ . If the abundance of $^{85} R b$ $""^85 Rb$ is 80.2% and the abundance of $^{87} R b$ $""^87 Rb$ is 19.8%, what is the average atomic mass of rubidium,?