Respuesta :
Answer:
The answer to your question is: 85.458 amu
Explanation:
data
Rubidium-85 A = 84.9118 amu abundance = 72.15%
Rubidium - 87 A = 86.9092 amu abundance = 27.85%
Atomic weight = ?
Atomic weight = 84.9118(0.7215) + 86.9092(0.2785)
Atomic weight = 61.2538 + 24.2042
Atomic weight = 85.458 amu
Rubidium has two naturally occurring isotopes, rubidium -85 ( atomic mass = 84.9118 amu; abundance = 72.15%) and rubidium -87 (atomic mass = 86.9092; abundance = 27.85%). The atomic weight of rubidium is 85.46 amu.
How to calculate the average atomic mass of element ?
To calculate the average atomic mass of element use this formula
Average Atomic Mass = f₁M₁ + f₂M₂
where,
f = Fraction of natural abundance of isotope
M = Mass number of isotope
Isotope Rubidium -85 (Atomic mass = 84.9118 amu and Abundance = 72.15)
Abundance = [tex]\frac{72.15}{100}[/tex]
= 0.7215
Isotope Rubidium- 87 (Atomic mass = 86.9092 amu and Abundance = 27.85%)
Abundance = [tex]\frac{27.85}{100}[/tex]
= 0.2785
Now put the value in above formula, we get:
Average Atomic Mass = f₁M₁ + f₂M₂
= (84.9118 × 0.7215) + (86.9092 × 0.2785)
= 61.26 + 24.20
= 85.46 amu
Thus from the above conclusion we can say that Rubidium has two naturally occurring isotopes, rubidium -85 ( atomic mass = 84.9118 amu; abundance = 72.15%) and rubidium -87 (atomic mass = 86.9092; abundance = 27.85%). The atomic weight of rubidium is 85.46 amu.
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