The relative abundances of the two isotopes of chlorine are shown in this table:
| Isotope | Relative Abundance | |———|——————–| |
35
Cl | 75% | |
37
Cl | 25% | Use this information to deduce the mass spectrum of chlorine gas.
The Correct Answer and Explanation is:
To deduce the mass spectrum of chlorine gas from the given isotopic abundances, we first need to understand the concept of isotopes and how they contribute to the overall mass spectrum of a compound.
Isotopes of Chlorine
Chlorine has two stable isotopes:
- Chlorine-35 (^35Cl): This isotope has an atomic mass of approximately 34.96885 amu (atomic mass units).
- Chlorine-37 (^37Cl): This isotope has an atomic mass of approximately 36.96590 amu.
Relative Abundance
From the provided data:
- ^35Cl has a relative abundance of 75%.
- ^37Cl has a relative abundance of 25%.
Mass Spectrum Analysis
In a mass spectrometer, the isotopes are separated based on their mass-to-charge ratio. The relative abundance of each isotope will determine the intensity of the peaks in the mass spectrum. Here’s how the spectrum would be calculated:
- Calculate the contributions of each isotope to the overall spectrum:
- For ^35Cl:
[
\text{Peak height} = 75\% \text{ (relative abundance)}
]
The peak corresponding to ^35Cl will appear at m/z (mass-to-charge ratio) of 35, with a height proportional to its abundance (75%). - For ^37Cl:
[
\text{Peak height} = 25\% \text{ (relative abundance)}
]
The peak for ^37Cl will appear at m/z of 37, with a height proportional to its abundance (25%).
- Constructing the Mass Spectrum:
- At m/z = 35, there will be a peak with approximately 75% intensity.
- At m/z = 37, there will be a peak with approximately 25% intensity.
Conclusion
The mass spectrum of chlorine gas will exhibit two prominent peaks:
- A significant peak at m/z = 35, representing the majority isotope (^35Cl).
- A smaller peak at m/z = 37, representing the less abundant isotope (^37Cl).
This mass spectrum effectively reflects the isotopic composition of chlorine, providing valuable information regarding its isotopic distribution, which is crucial for various applications in chemistry and analytical sciences, such as determining molecular structures, reaction pathways, and environmental studies. Understanding isotopic abundances through mass spectrometry can also aid in tracing the sources of chlorine in different contexts, from industrial applications to natural environments.