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Questions on Instrumental Methods of Analysis
1. Which one of the following techniques can be used for the detection in a liquid
chromatograph?
a. Ultraviolet absorbance or refractive index measurement.
b. Increase in temperature
c. Ionization in flame
d. Thermal conductivity
Answer = a
2. Considering high performance liquid chromatography, which one of the following
statements is FALSE?
a. HPLC is suitable for the separation and determination of the
nonvolatile (high boiling point) components.
b. The stationary phase could be a liquid or a solid.
c. Columns longer than 50 meters have been used here to
increase the efficiency of separation.
d. High pressure is used here to decrease the retention time and improve
the separation of components.
Answer = c
3. According to Beer’s law for a colored solution, which one of the following
statements is False?
(a) The percent transmission is not directly proportional to the concentration.
(b) The absorbance is directly proportional to the concentration.
(c) The absorbance does not change when the cell path length (cell
thickness) increases.
(d) When the concentration of the unknown sample is higher than the
highest concentration in the calibration range, the sample should be
diluted.
Answer = b
4. Deuterium and tungsten lamps are used as a light source in one of the
following techniques.
(a) Nuclear magnetic resonance spectrophotometers
(b) X-rays diffractometers
(c) Gas chromatograph
(d) Uv/Visible spectrophotometers
Answer = d
5. Which one of the following arrangements for the sequence of the main components of
a Uv/visible spectrophotometer is Correct?
(a) Light source Monochromator Sample cell Detector Readout
(b) Light source Detector Sample cell Monochromator Readout
(c) Light source Sample cell Detector Monochromator Readout
(d) Light source Readout Sample cell Detector Monochromator
Answer = a
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6. Considering the electrochmical cells, which one of the following statements is False?
(a) Galvanic cell is that in which a spontaneous chemical reaction takes place
and an electrical energy is produced.
(b) A nonspontaneous chemical reaction is forced to occur in the
electrolysis cell.
(c) The salt bridge is used to allow for the movement of electrons
from the solution of one half cell to the other
(d) The cathode is the electrode at which reduction takes place.
Answer = a
7. which one of the following radiation has the longer wavelength
a- infra red
b- visible
c- x-ray
d- ultra violet
e- gamma rays
Answer = a
8. The energy associated with infra red is enough to make
a- electronic transitions
b- vibrational and rotational transitions
c- a full separation of the electron in the outer shell
d- X-ray fluorescence
e- an electron move from an inner orbital
Answer = b
9. The moisture in an organic substance is determined by
a- potentiometric titration
b- X-ray fluorescence
c- X-ray absorption
d- Karl Fisher titration
e- Measuring the pH of the system
Answer = d
10. The technique used to identify a functional group in an organic molecule is
a- coulometry
b- X-ray fluorescence
c- Infrared spectrometry
d- Karl Fisher titration
e- Conductimetry
Answer = c
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11. One part per million is the same as
(a) 1 g/g
(b) 1 mg/kg
(c) 1 ng/mg
(d) All of the above are correct
Answer = c
12. Narrow line spectra are emitted by
(a) hot solids
(b) excited polyatomic molecules
(c) molecules in the ground molecular state
(d) excited atoms
Answer = d
13. What are the dimensions of the molar absorptivity in the Beer's law expression ?
(a) Moles per liter
(b) Liters per mol.centimeter
(c) Grams per mole
(d) Micrograms per square centimeter
Answer = b
14. The region of the electromagnetic spectrum in which the highest energy
photons are observed is the
(a) ultraviolet
(b) infrared
(c) microwave
(d) x-ray
Answer = d
14. An important advantage of a double-beam spectrophotometer over a single-beam
spectrophotometer is that
(a) it permits cancellation of slow variations of the source power
(b) it requires same light source for Uv, Vis, and Infra red radiation
(c) it can be used in conjunction with rapid response detection systems
(d) a greater range of wavelengths can be used
Answer = a
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15. Grating is a device used in the spectrophotometer to function as
(a) a light source
(b) a monochromator
(c) a detector
(d) a nebulizer
Answer = b
16. Helium rather than argon, often is used as the carrier gas in GLC when TCD is
used as the detector because,
(a) He has a higher ionization potential
(b) He is more inert
(c) He has stable isotopes which separate and cause a change in column
behavior.
(d) He has a higher thermal conductivity
Answer = d
17. To deionize laboratory water by ion-exchange, the best approach employs
(a) a column containing a strong acid cation exchanger in the hydrogen form
(b) a column containing a strong base anion exchanger in the hydroxyl form
(c) a mixed bed column containing a strong acid cation exchanger in the
sodium form and a strong base anion exchanger in the hydroxyl form
(d) a mixed bed column containing a strong acid cation exchanger in the
hydrogen form and a strong base anion exchanger in the hydroxyl form
Answer = c
18. Reversed phase HPLC is the technique in which
(a) stationary phase is solid and mobile phase is liquid.
(b) the stationary phase is made of very fine particles.
(c) the stationary phase is non polar and the mobile phase is relatively polar.
(d) the stationary phase has been silinized with dimethyldichlorosilane.
Answer = c
19. Considering high performance liquid chromatography, which one of the
Following statements is FALSE?
(a) HPLC is suitable for the separation and detrmination of the nonvolatile
species.
(b) The stationary phase used in the HPLC column could be relatively polar or
nonpolar liquid.
(c) The separation efficiency has been increased by decreasing the particle
size of the solid support for the stationary phase.
(d) Very long columns have been used here to increase the effecirncy of
separation.
Answer = d
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