For the molecule CBr4, the number of peaks which comprise the cluster for the molecular ion will be which of the following?a)1b)5c)4d)3Correct answer is option 'B'. Can you explain this answer?

Question

Answer

Ans: b

Explanation: Since bromine has two separate isotopes (79 and 81, with approximately the same proportions of each), the possibilities for different molecular masses will be those with four 79 isotopes, three 79 and one 81 isotope, two of each isotope, three 81s and one 79 isotopes, and four 81 isotopes - i.e. 5 in total.

Answer

Answer

The number of peaks in the mass spectrum of a molecule can provide valuable information about its structure and composition. In the case of CBr4, or carbon tetrabromide, the molecular ion will have five peaks.

- **Molecular Ion**
The molecular ion peak represents the intact molecular ion of the compound. It is the peak with the highest m/z (mass-to-charge ratio) value, as it corresponds to the entire molecule. In the case of CBr4, the molecular ion peak will have an m/z value corresponding to the sum of the atomic masses of carbon and four bromine atoms.

- **Isotopes**
Isotopes of an element have different masses due to the varying number of neutrons in their nuclei. Isotopes can contribute additional peaks in the mass spectrum. Carbon has two stable isotopes, carbon-12 (98.9%) and carbon-13 (1.1%), while bromine has two isotopes, bromine-79 (50.5%) and bromine-81 (49.5%). These isotopes can contribute to additional peaks in the spectrum.

- **Fragmentation**
Fragmentation occurs when the molecular ion breaks apart into smaller fragments during ionization. This can occur due to the ionization process itself or during the mass spectrometer's analysis. Fragmentation can result in peaks corresponding to the fragments produced.

- **Number of Peaks**
In the case of CBr4, the molecular ion will have five peaks. One peak corresponds to the intact molecular ion, and the other four peaks are due to the presence of the two carbon isotopes (C-12 and C-13) and the two bromine isotopes (Br-79 and Br-81). These isotopes contribute additional peaks in the spectrum.

Therefore, the correct answer is option B, which states that the number of peaks comprising the cluster for the molecular ion of CBr4 is 5.

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