The mass spectrum of element Z is shown.
What is element Z?
Correct Answer: \( \boxed{\mathrm{B}} \)
The spectrum shows two major peaks at approximately \(m/e=35\) and \(m/e=37\) in a ratio of about 3:1.
These correspond to the naturally occurring isotopes:
The additional peaks at \(m/e=70\), 72 and 74 are molecular ion peaks for \( \mathrm{Cl_2^+} \):
This characteristic pattern is unique to chlorine.
Therefore, the correct answer is (B).
The mass spectrum of an organic compound has the following features.
What could be the identity of the organic compound?
Correct Answer: \( \boxed{\mathrm{A}} \)
The molecular ion peak at \( m/e = 60 \) shows that the compound has a relative molecular mass of \(60\).
The peak at \( m/e = 61 \) has an intensity of about \(2.2\%\), indicating the presence of two carbon atoms, since the natural abundance of \(^{13}\mathrm{C}\) is approximately \(1.1\%\) per carbon atom.
There is no fragment peak at \( m/e = 17 \), so a hydroxyl group (\( \mathrm{-OH} \)) is unlikely. This rules out ethanoic acid and propan-2-ol.
A fragment at \( m/e = 31 \) is consistent with the \( \mathrm{CH_3O^+} \) ion, which is commonly produced by esters containing a methoxy group.
Methyl methanoate, \( \mathrm{HCOOCH_3} \), satisfies all of these observations.
Therefore, the correct answer is (A).
The mass spectrum of \( \mathrm{CH_3Cl} \) shows a molecular ion peak, \( \mathrm{M^+} \), at the \( \mathrm{m/e} \) value of \(50\) with a relative abundance of \(18.0\%\).
Other peaks are present in the mass spectrum.
What is seen in the mass spectrum at the \( \mathrm{m/e} \) value of \(52\)?
Correct Answer: \( \boxed{\mathrm{B}} \)
Chlorine has two common isotopes:
Therefore, the molecular ion peaks occur in the ratio \(3:1\).
If the \( \mathrm{M^+} \) peak at \( \mathrm{m/e}=50 \) has a relative abundance of \(18.0\%\), then the peak at \( \mathrm{m/e}=52 \) is:
\( \mathrm{18.0 \times \dfrac{1}{3}=6.0\%} \)
Therefore, the correct answer is (B).
