Massspectrometry is more often applied to molecules than to atoms. We will see in Chapter 3 that the molecular weight of a molecule is the sum of the atomic weights of the atoms in the molecule. The mass spectrum of H₂ is taken under conditions that prevent decomposition into H atoms. The two naturally occurring isotopes of hydrogen are ¹H (atomic mass = 1.00783 amu; abundance 99.9885%) and ²H (atomic mass = 2.01410; abundance 0.0115%). (c) Which peak will be the largest, and which the smallest?

Video transcript

Hi everyone here we have a question telling us, mass spectrometry can reveal the presence of isotopes of an element and a compound being analyzed. Isotopes as separate peaks can most easily be seen in abundance. Next to the molecular ion peak bro. Ming has two isotopes, bromine, 79 abundance 51%. And roaming 81 abundance 49%. If bromo methane ch three br is subjected to mass spectrometry, how will the roping isotopes appear on the mass spectrum? So the molecular mass of bromo methane using bro? Mean is 93 0. grams Permal using roaming 81. It is 95 .96 g per mole. There will be two peaks of equal intensity due to the almost equal abundance of the two broening isotopes, one at in Over Z- and the other at m oversee 96. And there will also be two more peaks, one at MZ and at m oversea 97. These are due to the presence of carbon 13, but these will be very small Compared to the peaks at 94 and 96 and that's because the abundance of carbon 13 is very low at 1.11%. So, this is our answer, thank you for watching. Bye.