Problem: 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.

FREE Expert Solution

atomic weight = [mass×f.a.]rubidum-85 + [mass×f.a.]rubidum-87


rubidium-85: atomic mass 84.9118 amu        f.a. = 72.15% ÷ 100 = 0.7215

rubidium-87: atomic mass 86.9092 amu      f.a. 27.85% ÷ 100 = 0.2785


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Problem Details

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.

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