C ORK I NSTITUTE OF T ECHNOLOGY
I NSTITI ÚID T EICNEOLA ÍOCHTA C HORCA Í
Semester 1 Examinations 2015/2016
Module Title:
Process Analytical Technology
Module Code:
PHYS8017
School:
Science & Informatics
Programme Title:
Bachelor of Science - Year 4
Programme Code:
SINEN 8 Y4, SPHYS 8 Y4, SCHQA 8 Y4
External Examiners(s):
Internal Examiners(s):
Dr J. Houlihan
Dr D. Goulding
Instructions:
Answer all questions. All questions carry equal marks. A table of scientific
constants is provided at the end of the exam paper.
Duration:
2 hours
Sitting:
Winter 2015
Requirements for this
examination:
Log Tables
Note to Candidates:
Please check the Programme Title and the Module Title to ensure that you have received the correct
examination paper. If in doubt please contact an Invigilator.
1. (a) Heated Neon gas is known to emit light with an energy of 1.8788 eV. Calculate the wavelength and
frequency of the emitted photons.
(5)
(b) Using the Rydberg formula, calculate the wavelength of the α and β spectral lines of the Lyman and
Balmer series for Hydrogen. Draw a simple sketch to illustrate the transitions in Hydrogen to which
these spectral lines correspond.
(5)
(c) List the main failing of the Rutherford model for the Hydrogen atom and state the main postulates
proposed by Bohr to overcome this failing.
(5)
(d) In Bohr’s model for the Hydrogen atom, the energy of the
En = −
nth
energy level is given by
13.6
eV
n2
and this energy level is found at a distance
rn = nrB
5.292 × 10−11
where rB =
m is the Bohr radius, from the nucleus. Calculate the energy, wavelength and
orbital radius for the n = 2 state of Hydrogen.
(5)
(e) Four quantum numbers can be used to describe the atom. List these quantum numbers, their allowed
values and what each quantum number represents. If you consider the quantum number n = 3, draw
a table indicating the various allowed energy states of the atom and describe the order in which these
energy levels are filled.
(5)
2. (a) What is the main requirement for a molecule to be considered IR active? Explain therefore why Oxygen,
Hydrogen and Nitrogen are considered not to be IR active.
(5)
(b) Draw a simplified schematic of a Fourier Transform infrared (FTIR) spectrometer.
(5)
(c) Describe the main advantages of an FTIR spectrometer over a dispersive IR spectrometer.
(5)
(d) The vibrational motion of a Carbon Nitrogen double bond (C=N) can be approximated as a harmonic
oscillator. Assume that the Carbon atom has a mass of 12 amu, the Nitrogen atom has a mass of 14 amu
and that the characteristic vibrational oscillation is found at a wavenumber of 1660 cm−1 . Calculate the
energy and wavelength of light required to excite this vibrational motion. Furthermore, find the bond
strength corresponding to the characteristic vibrational oscillation frequency of the C=N bond.
(5)
(e) A student creates a compound in the lab, the chemical formula for which is C4 H8 O2 . However the student
is uncertain whether they have created Ethyl Acetate or Acetoin. The structures for both Ethyl Acetate
and Acetoin are shown (Fig. 1 and Fig. 2) as is the IR spectrum measured (Fig. 3). By analysing the
measured IR spectrum, decide which compound was generated and provide a clear reasoning for your
answer.
(5)
3. (a) State Beer-Lambert’s Law and explain why it is preferential to use absorbance rather than percentage
transmittance as a measurement.
(5)
(b) Explain why absorption lines in spectroscopy are not delta like but rather have an associated broadened
lineshape.
(5)
(c) Explain the main differences between a magnetic sector mass analyser and a time of flight mass analyser.
Use diagrams and equations as required.
(5)
(d) In a magnetic sector mass spectrometer with a circular path radius of 0.3 m and a magnetic field of
strength 0.5 T, calculate the accelerating voltages required in order to measure mass to charge ratios
ranging from 1 amu to 750 amu. (You may assume that all of the ions are singly charged)
(5)
(e) A time of flight mass spectrometer has an extraction pulse voltage of 10 kV. If the length of the drift-free
region of the spectrometer is 0.35 m, calculate the time difference in the arrival of a singly charged and
doubly charged Carbon ion.
(5)
4. (a) Explain the difference between Rayleigh and Raman scattering. Using a simple energy level diagram,
draw energy transitions representing both Rayleigh and Raman scattering.
(5)
(b) Describe the advantages of Raman spectroscopy over infrared spectroscopy.
Page 2 of 4
(5)
Figure 1: Ethyl Acetate
Figure 2: Acetoin
Figure 3: Measured IR spectrum
(c) In 1 H proton NMR, describe the significance of the four features that you examine in an NMR spectrum.
Explain the cause of signal splitting in NMR spectra and provide a simple example for the observation
of single and triplet signals in such spectra.
13 C
s−1
67.262×106
(5)
T−1 ,
(d) If the gyromagnetic ratio of the
nuclei is
rad
calculate the frequency of precession of the proton in a magnetic field strength of 1.41 T. If the frequency of precession is now changed
to 600 MHz, calculate the required magnetic field strength required to obtain this precession frequency.
(5)
(e) The chemical structure for 1-chloropropane (C3 H7 Cl) is
H
Cl
H
H
C
C
C
H
H
H
H
and a measured 1 H proton NMR spectrum is shown in Fig. 4. Which features in the NMR spectrum can
be attributed to the different groups of Hydrogen atoms in the chemical structure? Copy the structure
and NMR spectrum to your answer book for reference.
Table of constants
1 eV
R
1 amu
1.6 × 10−19 J
1.09737 × 107 m−1
1.66 × 10−27 kg
h
c
Page 3 of 4
6.636 × 10−34 Js
3 × 108 m s−1
(5)
Figure 4: Measured NMR spectrum of 1-chloropropane
Page 4 of 4