Rubidium has two naturally occurring isotopes with masses of 84.91 amu and 86.91 amu and an atomic mass of 85.47 amu. Part A: Which mass spectrum is most likely to correspond to a naturally occurring sample of rubidium?

: To determine which mass spectrum is most likely to correspond to a naturally occurring sample of rubidium, we need to look at the relative abundances of the isotopes based on their atomic masses and the average atomic mass of rubidium.

First, let's understand what the mass spectrum would show us. The mass spectrum would have peaks at mass-to-charge ratios corresponding to the isotopes present. In the case of rubidium, we would have peaks at around 84.91 amu for rubidium-85 (\(^{85}Rb\)) and 86.91 amu for rubidium-87 (\(^{87}Rb\)).

Given the average atomic mass of rubidium is 85.47 amu, which is closer to the mass of \(^{85}Rb\), we can infer that \(^{85}Rb\) is more abundant than \(^{87}Rb\). So, the mass spectrum most likely to correspond to a naturally occurring sample of rubidium would show a higher peak at 84.91 amu than at 86.91 amu, indicating that \(^{85}Rb\) is the more abundant isotope in nature.