Problem: There are two different isotopes of bromine atoms. Under normal conditions, elemental bromine consists of Br2 molecules, and the mass of a Br2 molecule is the sum of the masses of the two atoms in the molecule. The mass spectrum of Br2 consists of three peaks: Mass (amu)  Relative Size157.8360.2569159.8340.4999161.8320.2431Determine the average molecular mass of a Br2 molecule.

FREE Expert Solution

We are asked to determine the average molecular mass of a Br2 molecule.

Mass spectroscopy is an analytical technique that plots ion signal (fractional abundance) as a function of mass-to-charge ratio.

We will solve for each atom’s average mass using their relative size (fractional abundance). 


The formula for average mass is:

Average mass = (Mass isotope × Fractional Abundance)

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Problem Details
There are two different isotopes of bromine atoms. Under normal conditions, elemental bromine consists of Br2 molecules, and the mass of a Br2 molecule is the sum of the masses of the two atoms in the molecule. The mass spectrum of Br2 consists of three peaks:


 Mass (amu Relative Size
157.8360.2569
159.8340.4999
161.8320.2431


Determine the average molecular mass of a Br2 molecule.

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