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 (a) What is the origin of each peak (of what isotopes does each consist)?

Verified step by step guidance

Step 1: Understand that the mass spectrum of Br₂ is showing the masses of the different isotopes of bromine. The three peaks represent the three different combinations of isotopes that can form a Br₂ molecule.

Step 2: Recognize that bromine has two isotopes: Br-79 and Br-81. The mass numbers of these isotopes are approximately 79 and 81 respectively.

Step 3: Realize that the second peak in the mass spectrum (159.834 amu) represents the mass of a Br₂ molecule made up of one Br-79 atom and one Br-81 atom. This is because the sum of the mass numbers of Br-79 and Br-81 is approximately 160, which is close to the mass of the second peak.

Step 4: Understand that the relative size of the peak (0.4999) indicates the relative abundance of Br₂ molecules made up of one Br-79 atom and one Br-81 atom. This is the most common combination of isotopes in a Br₂ molecule, which is why the second peak is the largest.

Step 5: Remember that the mass spectrum does not provide the exact masses of the isotopes, but rather their approximate masses. The exact masses of the isotopes can be determined using more precise methods.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.

Video duration:

Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Isotopes

Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons, resulting in different atomic masses. For bromine, the two stable isotopes are bromine-79 and bromine-81. Understanding isotopes is crucial for interpreting mass spectra, as the relative abundance of each isotope contributes to the overall mass of the molecule.

Mass Spectrum

A mass spectrum is a graphical representation of the mass-to-charge ratio of ions, which helps identify the composition of a sample. Each peak in the spectrum corresponds to a specific ion, with its height indicating the relative abundance. In the case of Br2, the peaks represent the different combinations of bromine isotopes, allowing us to deduce the isotopic composition of the molecule.

Molecular Mass Calculation

The molecular mass of a compound is calculated by summing the atomic masses of its constituent atoms. For Br2, the molecular mass is derived from the masses of the two bromine atoms, which can be isotopes. The second peak at 159.834 amu suggests a specific combination of isotopes, which can be determined by analyzing the contributions of each isotope to the total mass.

Recommended video:

Guided course

03:12

Molar Mass Calculation Example

Related Practice

Textbook Question

The element chromium (Cr) consists of four naturally occurring isotopes with atomic masses 49.9460, 51.9405, 52.9407, and 53.9389 u. The relative abundances of these four isotopes are 4.3, 83.8, 9.5, and 2.4%, respectively. From these data, calculate the atomic weight of chromium.

Textbook Question

Copper (Cu) consists of two naturally occurring isotopes with masses of 62.9296 and 64.9278 u. (a) How many protons and neutrons are in the nucleus of each isotope? Write the complete atomic symbol for each, showing the atomic number and mass number. (b) The average atomic mass of Cu is 63.55 u. Calculate the abundance of each isotope.

views

Textbook Question

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 (b) What is the mass of each isotope?

views

Textbook Question

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 (c) Determine the average molecular mass of a Br₂molecule.

Textbook Question