A bottle containing an unknown organic compound was examined in a university laboratory - VCE - SSCE Chemistry - Question 4 - 2016 - Paper 1
Question 4
A bottle containing an unknown organic compound was examined in a university laboratory. There was an incomplete label on the bottle that gave only the empirical for... show full transcript
Worked Solution & Example Answer:A bottle containing an unknown organic compound was examined in a university laboratory - VCE - SSCE Chemistry - Question 4 - 2016 - Paper 1
Step 1
On the diagram above, circle the base peak.
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Answer
The base peak in the mass spectrum is the peak with the highest intensity. In this case, the base peak is located at m/z = 30.
Step 2
At what m/z ratio is the principal peak that supports the chemist's hypothesis that the unknown compound has the formula NH₂CH₂CH₂NH₂? Justify your answer.
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Answer
The principal peak is at m/z = 60. This corresponds to the molecular ion of the compound NH₂CH₂CH₂NH₂. The molecular weight can be calculated as follows:
The formula consists of: 2 Nitrogen (N) = 2 g/mol, 4 Carbon (C) = 48 g/mol, and 10 Hydrogens (H) = 10 g/mol.
Thus, the total molar mass is:
extMolarMass=2+48+10=60extg/mol
This confirms that the m/z = 60 peak is indeed consistent with the hypothesized formula.
Step 3
Write the semi-structural formula of the species that produces the peak at 30 m/z.
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Answer
The semi-structural formula for the species that produces the peak at m/z = 30 is NH₂CH₂⁺. This represents the fragment ion produced during fragmentation in the mass spectrometer.
