A high-resolution mass spectrometer was used to analyze two gaseous samples

CHEMISTRY · Multi-part · A Level · Chemistry · Atomic structure · Atomic structure

Problem

A high-resolution mass spectrometer was used to analyze two gaseous samples, labeled Sample A and Sample B, each known to contain only chlorine atoms present as singly charged monatomic ions. The instrument reported the following relative intensities (in arbitrary units) for the two principal peaks observed.

m⁄z	Sample A intensity	Sample B intensity
35	756	620
37	244	380

(Natural chlorine consists of the isotopes

^{35}\text{Cl}

and

^{37}\text{Cl}

with percent abundances 75.78 % and 24.22 %, respectively.) (a) Describe two ways in which the mass spectra of Samples A and B differ from the spectrum that would be expected for naturally occurring chlorine. (b) Identify which sample is enriched in

^{37}\text{Cl}

relative to natural chlorine and justify your answer using the numerical data provided. (c) Estimate to the nearest whole percent the percent abundance of

^{37}\text{Cl}

in the enriched sample. (d) Explain, in terms of atomic mass and relative intensities, how the average atomic mass of chlorine in the enriched sample would compare with the standard atomic weight listed on the periodic table.

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