Mass Spectrometry and Atomic Identification (4E) Practice Test

An analytical lab uses a mass spectrometer to identify an unknown compound. The instrument detects ions, and neutral species are not observed. After a change in ion source settings, the total ion signal decreases substantially, but the $m/z$ positions of the remaining peaks are unchanged. The principle involved is that $m/z$ is determined by ion mass and charge, while signal intensity depends on the number of ions detected. Which conclusion about the ionization process is most consistent with these results? (Constants: $e=1.60\times10^{-19}\ \text{C}$.)

A lab analyzes a mixture containing chlorine using a mass spectrometer that produces mostly singly charged atomic ions. The spectrum shows two peaks at $m/z=35$ and $m/z=37$ with an intensity ratio of about 3:1. The principle involved is that isotopes of the same element have different masses but (here) the same charge, so their $m/z$ values differ by their mass difference. Which conclusion about the sample is most consistent with the data? (Constants: $e=1.60\times10^{-19}\ \text{C}$.)