Chemistry
Chemistry
Problem
A naturally occurring element X is found to have exactly two isotopes, X-29 and X-31. A mass spectrometer produces a spectrum that is described as follows: the peak at has an area that is four times the area of the peak at . Answer the following questions about element X. Assume all ions detected are singly charged monatomic ions. (a) Describe what information about the isotopic composition of element X can be inferred directly from the relative areas of the two peaks in the spectrum. (b) Without performing a numerical calculation, explain why the weighted average atomic mass of element X must be closer to 29 amu than to 31 amu. (c) Suppose a chemist enriches a sample so that the abundance ratio of X-29 : X-31 becomes 1.5 : 1. Predict qualitatively how the average atomic mass will change, and justify your prediction based on the definition of average atomic mass.Intuitive explanation
Isotope abundance is about reading the mass spectrum as a direct window into nature's inventory. The peak areas tell you the relative number of atoms of each isotope in your sample—taller peak means more atoms. Since the peak is four times larger than the peak, you have four times as many X-29 atoms as X-31 atoms. Use this ratio to calculate the weighted average atomic mass, then identify which element has that mass.
Intuitive explanation
Isotope abundance is about reading the mass spectrum as a direct window into nature's inventory. The peak areas tell you the relative number of atoms of each isotope in your sample—taller peak means more atoms. Since the peak is four times larger than the peak, you have four times as many X-29 atoms as X-31 atoms. Use this ratio to calculate the weighted average atomic mass, then identify which element has that mass.