Final answer:
The average atomic mass of rubidium can be calculated by multiplying the abundance of each isotope by its respective mass and summing the values. For rubidium-85 with 72.2% abundance and rubidium-87 with 27.8% abundance, the average atomic mass is 61.37 amu.
Step-by-step explanation:
The average atomic mass of rubidium can be calculated using the isotopic masses and abundances of its isotopes. Firstly, we convert the abundances to fractions by dividing them by 100. Then, we multiply the fraction of each isotope by its respective mass and sum the values. For rubidium, we have:
Isotope 85: 72.2% abundance, 85 amu mass
Isotope 87: 27.8% abundance, 87 amu mass
Converting the abundances to fractions, we get 0.722 for isotope 85 and 0.278 for isotope 87. Multiplying the fraction of each isotope by its mass, we get (0.722 × 85) + (0.278 × 87) = 61.37 amu.
Therefore, the average atomic mass of rubidium is 61.37 amu.