Use the mass spectrum of rubidium to determine the atomic mass of rubidium.

Verified step by step guidance

1. Identify the isotopes of rubidium from the mass spectrum. The m/z values are 203 and 205.
2. Note the relative intensities of each isotope. For m/z 203, the intensity is 41.89%, and for m/z 205, the intensity is 100%.
3. Convert the relative intensities to fractional abundances. For m/z 203, the fractional abundance is 41.89 / (41.89 + 100). For m/z 205, the fractional abundance is 100 / (41.89 + 100).
4. Calculate the weighted average atomic mass of rubidium using the formula: (fractional abundance of isotope 1 * mass of isotope 1) + (fractional abundance of isotope 2 * mass of isotope 2).
5. Substitute the values into the formula and solve for the atomic mass of rubidium.

Key Concepts

Mass Spectrum

A mass spectrum is a graphical representation of the mass-to-charge ratio (m/z) of ions. It displays the relative abundance of each ion detected, allowing chemists to identify the composition of a sample. Peaks in the spectrum correspond to different isotopes or molecular fragments, with their heights indicating the intensity or abundance of each ion.

Atomic Mass

Atomic mass is the weighted average mass of an element's isotopes, measured in atomic mass units (amu). It reflects both the mass and the relative abundance of each isotope present in a sample. To calculate the atomic mass from a mass spectrum, one must consider the m/z values and their corresponding intensity percentages to find a weighted average.

Isotopes

Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons, resulting in different atomic masses. For rubidium, the isotopes present in the mass spectrum are typically Rb-203, Rb-204, and Rb-205. Understanding isotopes is crucial for accurately determining the atomic mass from the mass spectrum, as each isotope contributes differently based on its abundance.