Mass Spectroscopy MCQ M.Sc. Chemistry third semester CHE-313

M. Sc. Second year Postgraduate degree course

Third Semester

CHE - 313 Structural Elucidation by Spectral methods

Mass Spectroscopy Introduction, ion production (EI, CI, FD and FAB), ion analysis, ion abundance, factors affecting on fragmentation, fragmentation of different functional groups, molecular ion peak, isotopic peaks, metastable peak, Nitrogen rule, McLafferty rearrangement, Retro Diels - Alder reaction.

1. In mass spectrometry 81Br shows:

(a) M+1 peak

(b) M+2 peak

(d) M+4 peak

2. Klystron is used as radiation source in

(a) X-ray diffraction

(b) Electron spin resonance

(c) Mass spectrometry

(d) None of above

3. In mass spectra, the most intense peak is the

(a) Base peak

(b) Metastable ion peak

(d) Rearrangement ion peak

4. Which of following ionization technique is used in molecular weight determination of large biomolecule by using mass?

(a) Electron impact

(b) Chemical ionization

(c) MALDI

(d) None of the above

5. A mass spectrometer bombards molecules with a high energy electron beam in

(a) Colloidal Phase

(b) Liquid Phase

(d) Vapour Phase

6. The inert gas used in the ionization stage of mass spectrometry is

(a) Helium

(b) rgon

(d) Methane

7. The correct order for the basic features of a mass spectrometer is _____________

(a) Acceleration, deflection, detection, ionization

(b) Ionisation, acceleration, deflection, detection

(d) Acceleration, deflection, ionisation, detection

8. Principal involved in mass spectrometer is

(a) Excitation of electron

(b) Electron impact bombardment

(d) Splitting of electrons magnetic energy

9. Separation of ions in mass spectrometer take place on the basis of which of the following?
a) Mass
b) Charge
c) Molecular weight
d) Mass to charge ratio

10. In mass spectroscopy positively charged ions can be produced by

(P) Heating the sample

(Q)Bombarding the sample with high energy electrons

(R) Bombarding the sample with high energy protons

(S) Chemical oonization

(a) Q, S

(b) Q, R

(d) P, S

11. In mass spectrum M-18 peak indicates loss of

(a) Hydroxyl group

(b) Hydrogen

(d) Water molecule

12. In mass spectrum of toluene, widely the Meta stable peak appear at

(a) 91 m/e

(b) 77 m/e

(c) 46.6 m/e

(d) 64.5 m/e

13. Metastable peaks have following all characteristics except

(a) These peaks are much broader that is they spread over mass units

(b) These peaks are of high intensity

(d) The meta stable ions can be detected by a double focusing mass spectrometer

14. Removal of a single electron from a molecule results in the formation of

(a) Fragment ion

(b) Metastable ion

(c) Molecular ion

(d) Rearrangement ion

15. Which of the following statement is false for mass spectroscopy?
(a) Mass spectroscopy is used to identify unknown compounds within a sample, and to elucidate the structure and chemical properties of different molecules
(b) Particle are characterized by their mass to charge ratios (m/z) and relative abundances
(c) This technique basically studies the effect of ionizing energy on molecules
(d) This technique can be used on all state of matter

16. In which state of matter mass spectroscopy is being performed?
(a) solid
(b) liquid
(c) gaseous
(d) plasma

17. Which species of the following is used to bombard with the sample for which mass spectroscopy has been performed?
(a) Alpha particles
(b) Neutrons
(c) Electrons
(d) Protons

18.In a time-of-flight mass spectrometer, the velocity v of an accelerated ion is related to its mass by which of the following?

(a) proportional to m (its mass)

(b) inversely proportional to its mass

(d) inversely proportional to the square root of its mass

19.Which of the following formulae is consistent with a molecular ion of m/z 73 in a mass spectrometry experiment?

(a) C₃H₈N₂

(b) C₄H₁₁N

(d) C₃H₅NO

20.An accurate mass measurement on a molecular ion peak gives the value of 72.0583. Identify the appropriate formula as one of the following.

(a)C₃H₄O₃

(b)C₄H₈O

(c)C₂H₄N₂O

(d)C₃H₈N₂

21.In the mass spectrum of the molecule phenol, C6H5OH, the approximate intensity of the peak at m/z 95, relative to the molecular ion at 94 will be which of the following?

(a) 94%

(b) 6.6%

(d) 7.0%

22.For the molecule CBr4, the number of peaks which comprise the cluster for the molecular ion will be which of the following?

(a) 1

(b) 4

(d) 3

23.In the mass spectrum of the molecule CBr4 (see preceding question) the relative intensities of the peaks in the molecular ion will be which of the following?

(a) 1:1:1:1:1

(b) 1:2:2:2:1

(d) 1:3:4:3:1

24.In the mass spectrum of the molecule benzyl alcohol (C6H5CH2OH), the base peak would be predicted to correspond to which of the following structures?

(a) C₆H₅⁺ (m/z 77)

(b) C₆H₅CH⁺OH (m/z 107)

(d) ⁺C₆H₄CH₂OH (m/z 107)

25.In the mass spectrum of the molecule ethyl propanoate, CH₃CH₂C(O)OCH₂CH₃ (molar mass 102), a typical peak would be expected from a McLafferty 'rearrangement/fragmentation.' This would be found at an m/z corresponding to which of the following?

(a) 29

(b) 74

(d) 87

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