Final answer:
The peak at m/z 42 in the mass spectrum of Kr is due to the presence of isotopes, which are atoms of the same element with different numbers of neutrons. The different isotopes of Kr have different masses, and when a Kr sample is analyzed using a mass spectrometer, the ions produced by each isotope will have different mass-to-charge ratios. The small peak at m/z 42 corresponds to the ions produced by one of the isotopes of Kr.
Step-by-step explanation:
The occurrence of a small peak with an m/z (mass to charge ratio) value of 42 in the mass spectrum of Kr can be explained by the presence of isotopes. Isotopes are atoms of the same element that have different numbers of neutrons. In the case of Kr, there are multiple isotopes, including Kr-78, Kr-80, Kr-82, and Kr-83, which contribute to the observed peak at m/z 42.
The different isotopes of an element have different masses, and when a Kr sample is analyzed using a mass spectrometer, the ions produced from each isotope will have different mass-to-charge ratios. The small peak at m/z 42 in the mass spectrum corresponds to the ions produced by one of the isotopes of Kr.
It's important to note that the abundance of each isotope in a sample can vary, which is why some peaks may be larger or smaller than others. The relative height of the peak gives an indication of the abundance of the isotope in the sample.