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 (u) Relative Size 157.836 0.2569 159.834 0.4999 161.832 0.2431 (d) Determine the average atomic mass of a bromine atom

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Hi everyone here we have a question telling us that sulfur has four naturally occurring stable isotopes, three of which, 32 sulfur 33 sulfur 34 sulfur are more abundant than the 4th. 36 cell. For the mass spectrum of hydrogen sulfide H two S. Contains three molecular ion peaks. We have 33.987172 which has a relative intensity of 94.99%. We have 34.986560 which has an intensity of 0.7500%. And lastly we have 35.982968 atomic mass units with the relative intensity of 4.250%. And our question here is what is the origin of the third peak? Which sulfur isotope does it arise from? So we're going to use the protium isotope which is denoted by one H. And it is the most common hydrogen isotope. So we're going to have one H. Two Sulfur and we're going to calculate its mass which is plus 32 equals 34. And then we have one h. 2, 33. Soft fur Equals 12 plus equals 35. And lastly we have one H. Two, 30 for sulfur Equals plus 34 Equals 36. And we're looking for which one of these is closest two. Our 3rd peak here Which is 35.982968. And the closest one to that would be 34 S. Because it has atomic mass unit of 36, which is the closest to 35.982968. So that is our final answer. Thank you for watching. Bye.

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Key Concepts

Isotopes

Mass Spectrum

Average Atomic Mass Calculation