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Chemical Technician > Laboratory Technology & Acids/Bases > Flashcards

Laboratory Technology & Acids/Bases Flashcards

1
Q

Which is not a volumetric glassware?

a. beaker
b. burette
c. pipette
d. volumetric flask

A

a. beaker

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2
Q

Ambient laboratory conditions are not the same to standard conditions, therefore the volumes
dispensed in volumetric glassware are often not the same as the manufacturer’s specifications, but
within some acceptable limits determined by the manufacturer. This slight variation in volume
will cause a error that are based on volume-volume or mass-volume concentrations.
a. random
b. systematic
c. gross
d. all of the above

A

b. systematic

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3
Q

Glass cuvettes are typically for use in the wavelength range of visible light, whereas fused quartz
tends to be used for applications.

a. microwave
b. IR
c. uv/visible
d. none of the above

A

c. uv/visible

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4
Q

In this column type, the retention is governed by the interaction of the polar parts of the stationary
phase and solute.
a. reverse phase
b. ion exchange
c. column guard
d. normal phase

A

d. normal phase

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5
Q

A stable light source in AAS analysis, which is necessary to emit the sharp characteristic spectrum
of the element to be determined
a. Tungsten lamp
b. hollow cathode lamp
c. deuterium lamp
d. Nerst blower

A

b. hollow cathode lamp

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6
Q

The HPLC column type in which molecules are separated according to size.
a. Ion exchange
b. size exclusion
c. normal phase
d. reverse phase

A

b. size exclusion

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7
Q

Non Polar Reverse phase and C8 (octyl bonded silica) are commonly used for hydrophobic
Analytes in solid phase extraction. An example is
a. C18 (octadecyl bonded silica)
b. Resins
c. Florisil
d. alumina

A

a. C18 (octadecyl bonded silica)

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8
Q

Filters that can be heated and used in gravimetric analysis.
a. ordinary filter paper
b. GFF
c. Sintered glass fibers
d. none of the above

A

b. GFF

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9
Q

Objects cannot be weighed when hot or warm. But if you were to take a sample out and wait for it to cool it would pick up moisture like that so put it in
.
a. an oven
b. a dessicator
c. at room temperature
d. fumehood

A

b. a dessicator

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10
Q

Weighing to constant weight means a weighing difference of ±0.1mg using a calibrated
analytical balance.
a. ±1.0 mg
b. ±0.01g
c. ±0.01mg
d. ±0.1mg

A

d. ±0.1mg

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11
Q

The following are common desiccants except for

a. Calcium Sulfate
b. Ammonium Acetate
c. Calcium Chloride
d. Magnesium Oxide

A

b. Ammonium Acetate

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12
Q

During ignition for ashing, muffle furnaces that go up to 1100o
C are used primarily for this and
is needed to contain the sample.
a. porcelain crucible
b. evaporating dish
c. beaker
d. all of the above

A

a. porcelain crucible

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13
Q

In making standard solutions, are used for measuring liquid with high accuracy.
a. beakers
b. volumetric flasks
c. Erlenmeyer flasks
d. Nesslers Tubes

A

b. volumetric flasks

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14
Q

Used for distillation or heating of liquids, allows uniform heating.
a. round bottom flask
b. Erlenmeyer flask
c. test tube
d. Florence flask

A

a. round bottom flask

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15
Q

Most popular burettes are 10 mL, 25 mL and 50 mL types. Which has the highest resolution?

a. 25 mL
b. 10 mL
c. 50 mL
d. All of the above

A

c. 50 mL

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16
Q

Used for vacuum filtration using filter paper.
a. gooch crucible
b. Buchner funnel
c. rotary evaporator
d. rubber aspirator

A

b. Buchner funnel

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17
Q

In chromatography, is carried out on glass plates or strips of plastic or metal coated
on one side with a thin layer of adsorbent.

a. HPLC
b. GC
c. Paper Chromatography
d. Thin Layer Chromatography

A

d. Thin Layer Chromatography

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18
Q

The nominal volume of water (or mercury) contained, or delivered by an article of volumetric glassware,
at its reference temperature.
a. capacity
b. liter
c. mL
d. uL

A

a. capacity

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19
Q

In verification of laboratory glassware, is usually measured in terms of the tolerance,
which is the uncertainty in a measurement made with the glassware. Class A volumetric
glassware has a lower tolerance than Class B.

a. mean
b. accuracy
c. difference
d. precision

A

b. accuracy

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20
Q

Glass apparatus that are generally received with calibration certificates from suppliers.
a. Class B
b. Class A
c. Erlenmeyer flasks
d. Beakers

A

b. Class A

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21
Q

All proteins absorb electromagnetic radiation of wavelength around 190 nm, which corresponds
to a excitation in the protein molecule. In which region of the spectrum is this wavelength found?

a. X-ray
b. ultraviolet
c. Visible
d. Infrared

A

b. ultraviolet

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22
Q

Chromatography is used to

a. Separate two or more compounds based on their polarities.
b. Separate two or more compounds based on their masses.
c. Separate two or more compounds based on how strongly they interact with other
compounds.
d) all of the above

A

d) all of the above

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23
Q

A food scientist has a sample of a plantoil and wants to determine if the oil contains saturated or
unsaturated fatty acids. Which of the following spectroscopic techniques would be most
useful for this purpose?

a. ultraviolet spectroscopy
b. visible spectroscopy
c. infrared spectroscopy
d. mass spectroscopy

A

c. infrared spectroscopy

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24
Q

The concentration at which the calibration curve departs from linearity by a specified amount.
a. Limit of Blank
b. Dynamic Range
c. Limit of Linearity
d. Limit of quantitation

A

c. Limit of Linearity

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25
Q

A graphical representation of measuring signal as a function of quantity of analyte.
a. Calibration curve
b. Quality Control Chart
c. Absorbance Chart
d. None of the above

A

a. Calibration curve

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26
Q

What is the path of light through a spectrophotometer?

a. meter, photodetector, filter, sample, light source
b. meter, filter sample, photodetector, light source
c. light source, filter, sample, photodetector, meter
d. light source, sample, filter, photodetector, meter

A

c. light source, filter, sample, photodetector, meter

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27
Q

With a “standard” sample with a known absorbance and concentration and a measured absorbance, it is
easy to determine an unknown concentration of †the same substance by.

a. Beer’s Law
b. Beer and Lambert’s Law
c. Law of mass conservation
d. none of the above

A

a. Beer’s Law

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28
Q

The highest apparent analyte concentration expected to be found when replicates of a blank sample
containing no analyte are tested.

a. Limit of Detection
b. Limit of Blank
c. Limit of Linearity
d. Limit of Quantitation

A

b. Limit of Blank

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29
Q

Motion of the mobile phase through the stationary phase.
a. Elution
b. Retention time
c. Eluent
d. Elution time

A

a. Elution

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30
Q

A phase which sample is dissolved in may be gas, liquid, or supercritical fluid

a. stationary phase
b. reverse phase
c. normal phase
d. mobile phase

A

d. mobile phase

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31
Q

In spectrophotometric methods, the isolates the specific spectrum line emitted by
the light source through spectral dispersion.

a. monochromator
b. prism
c. sample compartment
d. detector

A

a. monochromator

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32
Q

In AAS method, If the sample concentration is too high to permit accurate analysis in linearity
response range, there are alternatives that may help bring the absorbance into the optimum
working range.

a. sample dilution
b. using an alternative wavelength having a lower absorptivity
c. reducing the path length by rotating the burner hand
d. All of the above

A

d. All of the above

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33
Q

A technique for separating mixtures into their components in order to analyze, identify, purify, and/or
quantify the mixture or components.
a. Spectroscopy
b. Chromatography
c. Gravimetry
d. Titrimetry

A

b. Chromatography

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34
Q

A “modified” stationary phase where polar solutes run fast i.e. reverse order.
a. Normal phase
b. Reverse phase
c. mobile phase
d. none of the above

A

b. Reverse phase

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35
Q

A graph showing the detectors response as a function of elution time : band’s shapes, position,
resolution
a. monitor display
b. quality control chart
c. calibration curve
d. chromatogram

A

d. chromatogram

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36
Q

The pH meter glass probe has two electrodes, one is a glass sensor electrode and the
other is a electrode.
a. reference
b. anode
c. cathode
d. none of the above

A

a. reference

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37
Q

Conductivity could be determined using the distance between the electrodes and theirsurface area using
Ohm’s law but, for accuracy, a calibration is employed using of well-known conductivity.
a. acid solution
b. basic solution
c. electrolytes
d. buffer solution

A

c. electrolytes

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38
Q

The electrical conductivity of water is directly related to the concentration of dissolved ionized
solids in the water or
a. Total Suspended Solids
b. Total Dissolved Solids
c. Volatile Solids
d. Total Solids

A

b. Total Dissolved Solids

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39
Q

The light source used in the visible range to 340-1000 nm.
a.deuterium
b. nerst blower
c. tungsten
d.incandescent

A

c. tungsten

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40
Q

A student has to measure out 9.40 mL of a liquid and selects a 100 mL graduated cylinder. To
improve the accuracy of the measurement, it would be most
effective to:

a. take the average of multiple measurements using the graduated cylinder.
b. measure the liquid using a 25 mL graduated cylinder instead.
c. estimate the measurement obtained from the graduated cylinder to an additional
significant figure.
d. measure the liquid using a 10 mL graduated pipette instead.

A

d. measure the liquid using a 10 mL graduated pipette instead.

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41
Q

Under the Bronsted concept of acids and bases, a base is
A. a proton donor
B. a proton acceptor
C. a hydroxide donor
D. an electron pair donor

A

B. a proton acceptor

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42
Q

Under the Lewis concept of acids and bases, an acid is
A. a proton donor
B. a proton acceptor
C. An electron pair donor
D. an electron pair acceptor

A

D. an electron pair acceptor

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43
Q

Under the Bronsted concept of acids and bases, an acid is
A. a proton donor
B. a proton acceptor
C. an electron pair donor
D. an electron pair acceptor

A

A. a proton donor

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44
Q

Which of the following is NOT an acid-base conjugate pair?
A. HCN and CN−
B. H2O and OH−
C. H2S and OH−
D. NH3 and NH4
+

A

C. H2S and OH−

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45
Q

Predict the products of the following acid-base reaction:HCl(aq) + NaOH(aq) →

A. H3O+
(aq) + OH−
B. Na+
(aq) + Cl−
(aq)
C. NaCl(aq) + H2O(l)
D. no reaction takes place

A

C. NaCl(aq) + H2O(l)

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46
Q

Predict the products of the following acid-base reaction: NH3(aq) + HNO3(aq) →

A. NH2OH(aq) + HNO2(aq)
B. NH4NO3(aq)
C. NH4OH(aq)
D. no reaction takes place

A

B. NH4NO3(aq)

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47
Q

What effect will addition of excess of HCl have on the pH of a solution of NH3?

A. increase the pH
B. decrease the pH
C. no effect
D. cannot tell from information given

A

B. decrease the pH

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48
Q

What effect will addition of sodium acetate have on the pH of a solution of acetic acid?
A. increase the pH
B. decrease the pH
C. no effect
D. cannot tell from information given

A

A. increase the pH

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49
Q

A solution that causes only a relatively small change in pH upon addition of small amounts of acids and bases is
A. saturated
B. a salt
C. a buffer
D. unsaturated

A

C. a buffer

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50
Q

Which of the following is buffer?

NaCl/NH4Cl
NH3/NH4Cl
NH3/CH3COOH
CH3COOH/NaOH

A

NH3/NH4Cl

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51
Q

A buffer solution may be a mixture of

A. a weak acid and its salt
B. a weak base and its salt
C. an excess of a weak acid with a strong base
D. all of the above

A
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52
Q

The conjugate base of acetic acid is
A. HCOOH
B. NH3
C. CH3COO−
D. OH−

A

C. CH3COO−

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53
Q

The conjugate acid of ammonia is
A. H3O+
B. NH4+
C. HCOOH
D. OH−

A

B. NH4+

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54
Q

. Effect produced by an ion, say from a salt, which is the same ion produced by the dissociation of a weak acid or
base is called
A. colloidal effect
B. precipitation effect
C. common ion effect
D. ligand effect

A

C. common ion effect

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55
Q

A principle stating that if stress is applied to a system at equilibrium, the equilibrium is shifted in the
direction that tends to reduce the stress.

A. Heisenberg Uncertainty Principle
B. Le Chatelier’s Principle
C. Hund’s Rule
D. Debye-Huckel Principle

A

B. Le Chatelier’s Principle

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56
Q

Water cannot function as which one of the following?

A. a Bronsted acid
B. a Bronsted base
C. a Lewis acid
D. a Lewis base

A

C. a Lewis acid

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57
Q

HCOOK is a/an
A. acid
B. base
C. salt
D. oxide

A

C. salt

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58
Q

When a strong acid is titrated with a weak base, the pH at the equivalence point is
A. basic
B. acidic
C. neutral
D. none of the above

A

B. acidic

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59
Q

When a strong acid is titrated with a strong base, the pH at the equivalence point is
A. basic
B. acidic
C. neutral
D. none of the above

A

C. neutral

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60
Q

When NH4Cl hydrolyzes, the resulting solution is
A. acidic
B. basic
C. neutral
D. none of the above

A

A. acidic

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61
Q

Acids and Bases Which statement is true?

a. The value of the equilibrium constant increases with the addition of a catalyst
b. A catalyst speeds up both the forward and reverse reaction rates
c. The greater the activation energy, the faster the rate of reaction.
d. A catalyst increases the rate of reaction by decreasing the number of collisions

A

b. A catalyst speeds up both the forward and reverse reaction rates

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62
Q

The lining of the stomach contains cells that secrete a solution of HCl. Which drink would best alleviate
heartburn (excess acid in the stomach)?

a. milk, pH = 6.5
b. wine, pH = 3.8
c. diet soda, pH = 4.3
d. milk of magnesia, pH = 10.5

A

d. milk of magnesia, pH = 10.5

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63
Q

Which species are acting as Bronsted acids in the reaction below?
HSO − (aq) + H O(l) ⇄ H O+ (aq) + SO −2(aq)

a. H2O
b. H2O and H3O+
c. H2O and SO −2
d. HSO4 − and H3O+

A

d. HSO4 − and H3O+

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64
Q

Which equation correctly describes the relationship between Kb and Ka for a conjugate acid/base pair?
a. Kb = Kw Ka
b. Kb = Ka / Kw
c. Kb = Kw / Ka
d. Kb = Ka + Kw

A

c. Kb = Kw / Ka

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65
Q

The following will cause drift errors in an analytical balance EXCEPT

A. Balance door is open.
B. Balance is not leveled.
C. Air currents are present in the laboratory.
D. Temperature of the balance and the sample to be weighed is the same

A

D. Temperature of the balance and the sample to be weighed is the same

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66
Q

Objects cannot be weighed when hot or warm. But if you were to take a sample out and wait for it to cool it would pick up moisture so it should be placed in a/an/at
A. oven
B. desiccator
C. room temperature
D. fume hood

A

B. desiccator

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67
Q

It is the nominal volume of water (or mercury) contained, or delivered by an article of volumetric glassware, at its reference temperature.
A. accuracy
B. calibration
C. capacity
D. measurand

A

C. capacity

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68
Q

A student is tasked to measure 12 mL of a liquid as precisely as possible. Which measuring device should be selected for this task?
A. 25 mL beaker
B. 25 mL graduated cylinder
C. 25 mL conical flask
D. 25 mL volumetric flask

A

B. 25 mL graduated cylinder

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69
Q

Which of the following is TRUE about TC pipets?

A. TC means “to carry”.
B. It commonly does not have a colored band.
C. It is used if the liquid left in the pipet is already accounted.
D. None of the above.

A

D. None of the above.

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70
Q

A student needs to transfer his precipitant from the beaker to the filter paper. Which of the following would be the best procedure in order to ensure a quantitative transfer of the precipitate?

A. Most of the supernatant liquid is decanted then bulk of precipitate is transferred to filter paper through a stirring rod, then the beaker is washed Ab with large volumes of wash solution.
B. Most of the supernatant liquid decanted first, then bulk of the precipitate is transferred through a stirring rod. The beaker is washed several times with small volumes of wash solution.
C. Solution is shaken, then immediately filtered; beaker is washed with big volumes of wash solution.
D. None of the above.

A

B. Most of the supernatant liquid decanted first, then bulk of the precipitate is transferred through a stirring rod. The beaker is washed several times with small volumes of wash solution.

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71
Q

To determine the density of a liquid, which of the following should be used?
A. graduated cylinder
B. volumetric flask
C. pycnometer
D. pipette

A

C. pycnometer

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72
Q

Which is TRUE for a 19/22 stopper?

A. radius=19 mm, height = 22 mm
B. radius = 22 mm, height = 19 mm 19/22
C. diameter = 19 mm, height = 22 mm
D. diameter = 22 mm, height = 19 mm

A

C. diameter = 19 mm, height = 22 mm

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73
Q

Which technique is recommended for determining the odor of an unknown liquid in the laboratory?

A. Hold a test tube of the liquid under the nose and inhale the vapor.
B. Transfer a few drops of the liquid to the bench top and inhale the vapor from there.
C. Use a dropper to collect a small quantity of the vapor and squirt this under the nose while inhaling.
D. Use a hand to fan some of the vapor from the test tube to the nose and inhale.

A

D. Use a hand to fan some of the vapor from the test tube to the nose and inhale.

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74
Q

The size of the sample taken for analysis depends on the
A. concentration of analyte
B. equipment to be used
C. specific chemical tests
D. all of the above

A

D. all of the above

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75
Q

Possible sources of contamination during sample preparation include
A. reagents
B. glassware from previous experiment
C. equipment from previous experiment
D. all of the above

A

D. all of the above

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76
Q

Which of the following can cause errors during the sample preparation?
I. Loss of sample during weighing or dissolution.
II. Contamination by impurities in reagents and in the environment.
III. Changes in mass due to varying humidity and temperature.
IV.Obtaining non homogeneous sample from the bulk.

A. I and II only
B. I, III, and IV
C. I, II, and III
D. I, II, III, and IV

A

D. I, II, III, and IV

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77
Q

Method of passing the sample through a metal or plastic mesh of a uniform cross-sectional area to separate particles into uniform sizes.
A. sieving
B. milling
C. pulverizing
D. macerating

A

A. sieving

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78
Q

Which of the following can remove a fairly large amount of water from a sample that contains thermally labile material?
A. hotplate
B. freeze dryer
C. convection oven
D. microwave equipment

A

B. freeze dryer

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79
Q

Sample preparation technique used prior to instrumental analysis of metals.
A. sieving
B. clean-up
C. acid digestion
D. liquid-liquid extraction

A

C. acid digestion

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80
Q

Which of the following should NOT be used during dry ashing?
A. Zirconium
B. Platinum
C. Porcelain
D. Glass

A

D. Glass

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81
Q

In an experiment to determine the percentage of water in a solid hydrate by heating, what is the best indication that all the water has been removed?
A. The solid melts.
B. The solid changes color.
C. Water vapor no longer appears.
D. Successive weighings give the same mass.

A

D. Successive weighings give the same mass.

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82
Q

Which of the following statement(s) is (are) TRUE?
l. Dry ashing is primarily for proximate composition and for some types of specific mineral analyses. II. Wet ashing is done as a preparation for the analysis of certain minerals.
III. Microwave systems are now available for both dry and wet ashing to speed the processes.
A. I only
B. ll only
C. I and II only
D. I, II, and III

A

D. I, II, and III

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83
Q

In the decomposition and dissolution of solids, which of the following is expensive and often the last resort?
A. fusion technique
B. simple dissolution
C. acid treatment using oxidation ds during sample preparation
D. dissolution using ultrasound and solvent

A

A. fusion technique

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84
Q

All of the following are properties of an organic solvent for extraction EXCEPT
A. dissolve the desired substance
B. react with the desired substance
C. not react or be miscible with water
D. has a low boiling point so it can be easily removed at a later purification step

A

B. react with the desired substance

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85
Q

This is done during liquid-liquid extraction to release the pressure build-up inside the separatory funnel during shaking.
A. stirring
B. venting
C. drawing
D. salting out

A

B. venting

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86
Q

Which of the following should NOT be done when an emulsion is formed during extraction?
A. stirring the emulsion gently using a stirring rod
B. adding salt crystals to the mixture and then stirring it gently
C. adding a salt solution to the mixture and then stirring it gently
D. shaking the separatory funnel containing the mixture very vigorously

A

D. shaking the separatory funnel containing the mixture very vigorously

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87
Q

In liquid-liquid extraction, it is often necessary to determine the aqueous and organic layers. To test the layers, a drop of water can be added to the top layer. If the drop of water dissolves in the top layer, then the top layer is
A. organic
B. aqueous
C. denser
D. nonaqueous

A

B. aqueous

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88
Q

This is used to remove trace amounts of water in organic solutions. This can be added to the by pooled organic layers before removal of the organic solvent.
A. drying agent
B. boiling stone
C. seed crystal
D. none of the above

A

A. drying agent

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89
Q

A 5-g organic solid is dissolved in 100 mL of distilled water. What is the best way to recover most of the organic solid?
A. Single extraction using 150 mL ether.
B. Single extraction using 150 mL acetic acid
C. Multiple extraction using three 50-mL portions of ether.
D. Multiple extraction using three 50-mL portions of acetic acid.

A

C. Multiple extraction using three 50-mL portions of ether.

90
Q

Which of the following is/are considered in purification using crystallization?
I. Polarity
II. Solubility
III. Vapor pressure

A. I only
B. II only
C. I and II only
D. I, II, and III

A

C. I and II only

91
Q

Which of the following funnels should be used to filter hot mother liquor during recrystallization?
A. Hirsch funnel
B. Büchner funnel
C. long stem funnel
D. short stem funnel

A

D. short stem funnel

91
Q

In crystallization, crystal phases can be interconverted by varying
a. Temperature
B. pressure
C. viscosity
D. size

A

a. Temperature

92
Q

Which of the following techniques can be used to heat a reaction to 200°C?
A. Use a Bunsen burner to heat the reaction vessel.
B. Use a heating mantle with stirring.
C. Place the reaction vessel in a sand bath with stirring.
D. Place the reaction vessel in a water bath with stirring.

A

C. Place the reaction vessel in a sand bath with stirring.

93
Q

All of the following statements are TRUE, EXCEPT
A. Two different pure substances have similar melting points.
B. An impure sample of a substance has a wider melting point range
C. Melting point serves as an index of purity of a solid crystalline substance.
D. Every pure solid crystalline substance has a characteristic and unique melting point.

A

A. Two different pure substances have similar melting points.

94
Q

Which of the following can promote even boiling?
A. stones
B. chips
C. stir bars
D. all of the above

A

D. all of the above

95
Q

Where should a thermometer be placed to determine the boiling point of the distillate?
A. inside the distilling flask and it should be just below the side arm of the flask
B. inside the distilling flask and it should be immersed in the mixture being distilled
C. inside the receiver
D. inside the adapter

A

A. inside the distilling flask and it should be just below the side arm of the flask

96
Q

An organic compound decomposes at its boiling point. What is the most appropriate method for the recovery of the solid organic compound?
A. steam distillation
B. vacuum distillation
C. fractional distillation
D. liquid-liquid extraction

A

A. steam distillation

97
Q

It allows for many successive distillations to take place at once. It contains indentations or a packing material with lots of surface area.
A. adapter
B. condenser
C. round bottom flask
D. fractionating column

A

D. fractionating column

98
Q

The boiling point of a liquid is the temperature at which the vapor pressure is
A. lesser than internal pressure
B. equal to internal pressure
C. equal to external pressure
D. greater than internal pressure

A

C. equal to external pressure

99
Q

When the solid and liquid phases are in equilibrium, the temperature of the system
A. decreases gradually
B. none of the given answers
C. increases gradually
D. remains constant

A

D. remains constant

100
Q

A liquid mixture that has a constant boiling point and whose vapor has the same composition as the liquid.
A.azeotrope
B. ideal
C. non-ideal solution
D. eutectic mixture

A

A.azeotrope

101
Q

What is the main purpose of heating under reflux?
A. To provide a very high temperature so that slow reactions occur at faster rates.
B. To increase the rate of evaporation of the solvent to increase the product yield.
C. To heat the reaction mixture in a solvent at a constant temperature without the loss of any reagents.
D. all of the above.

A

C. To heat the reaction mixture in a solvent at a constant temperature without the loss of any reagents.

102
Q

A reaction mixture needs to be cooled to -77°C after refluxing. Which of the following is the best method to be used?
A. Place the reaction vessel in an ice bath.
B. Place the reaction vessel in the freezer.
C. Place the reaction vessel in a salt and crushed ice mixture.
D. Place the reaction mixture in a dry ice-acetone mixture.

A

D. Place tie reaction mixture in a dry ice-acetone mixture.

103
Q

Which of the following statements about columns containing more theoretical plates is TRUE?
A. Columns containing more theoretical plates make separations impossible.
B. Columns containing more theoretical plates interact irreversibly with the analyte.
C. Columns containing more theoretical plates take a long time to perform separations.
D. Columns containing more theoretical plates are better suited to separate a complex mixture.

A

D. Columns containing more theoretical plates are better suited to separate a complex mixture.

104
Q

The height equivalent of a theoretical plate or HET following characteristics EXCEPT
A. It is defined by the van Deemter equation.
B. Equilibrium is attained at each height equivalent.
C. The smaller the value is, the better the separation attainable.
D. This quantity times column length is equal to the number of theoretical plates in the column.

A

D. This quantity times column length is equal to the number of theoretical plates in the column.

105
Q

In this chromatographic method, the sample may be gas or liquid injected into a gaseous mobile phase.
A. gas chromatography
B. affinity chromatography
C. thin layer chromatography
D. high pressure chromatography

A

A. gas chromatography

106
Q

The following are properties of an open tubular or capillary column EXCEPT

A. Poor resolution can be obtained.
B. Only small samples can be applied
C. It has a long column length with small inner diameter.
D. It has a large number of plates that permit rapid separations of closely related species

A

A. Poor resolution can be obtained.

107
Q

An air sample is subjected to gas chromatography for the analysis of Freon-11 (CCIF). The detector that is most suitable for this analysis is
A. TCD
B. ECD
C. FID
D. TSD

A

B. ECD

108
Q

Analysis and separation of industrial products like soap and synthetic detergents is done using
A. Thin layer chromatography
B. Gas chromatography
C. Partition chromatography
D. Ion exchange chromatograph

A

B. Gas chromatography

109
Q

An advantage of HPLC over GC for the separation and measurement of high molecular weight compounds is that
A. HPLC columns and detectors are simpler and less expensive.
B. The preparation of volatile derivatives is not necessary in HPLC.
C. HPLC systems are always operated under constant conditions of eluent temp and composition
D. The sensitivity of HPLC detectors increases as the molecular weights of the compounds increase.

A

B. The preparation of volatile derivatives is not necessary in HPLC.

110
Q

Which of the following is NOT an application of high performance liquid chromatography?
A. Separation of pharmaceutical drugs
B. Analysis of proteins, drugs and explosives
C. Separation of lipids, fatty acids and steroids
D. Elimination of undesirable substances from blood

A

D. Elimination of undesirable substances from blood

111
Q

It is the more common form of HPLC where the stationary phase is nonpolar and the mobile phase is polar.
A. affinity
B. exclusion
C. normal-phase
D. reversed-phase

A

D. reversed-phase

112
Q

Ion exchange particles carry fixed positive or negative charges. A sulfonic acid type resin has SO, H groups were H* can be exchanged for
A. cations
B. anions
C. small cations and large anions
D. small anions and large cations

A

A. cations

113
Q

The correct order in which light passes through a UV-Vis spectrophotometer?
A. detector, sample, source, monochromator
B. source, monochromator, sample, detector
C. source, sample, monochromator, detector
D. monochromator, source, sample, detector

A

B. source, monochromator, sample, detector

114
Q

What is the purpose of a monochromator?
A. To remove stray light from the room.
B. To serve as a polychromatic light source.
C. To focus light from the sample onto the detector.
D. To allow only light of a certain wavelength to pass from the source to the sample.

A

D. To allow only light of a certain wavelength to pass from the source to the sample.

115
Q

Which of the following demonstrates proper drying of cuvette?
A. dry using a desiccator
B. place in an oven to dry overnight
C. blot on absorbing towel or tissue paper and allow to air dry
D. none of the above

A

C. blot on absorbing towel or tissue paper and allow to air dry

116
Q

Which of the following is NOT a limitation of Beer’s law?
A. Light must be of a narrow wavelength range and preferably monochromatic.
B. Presence of fluorescent species in solution may interfere in the final absorbance of solution.
C. At high concentration, molecules may polymerize, affecting the absorption of solution.
D. Beer’s law does not form the quantitative basis for all types of absorption spectroscopy.

A

D. Beer’s law does not form the quantitative basis for all types of absorption spectroscopy.

117
Q

Widely used continuous atomization method in AAS. It is also the most reproducible of all liquid-sample introduction methods that have been developed for AAS to date.
A. Flame
B. Electrothermal
C. Direct-current plasma
D. Inductively coupled plasma

A

A. Flame

118
Q

A hollow cathode tube lamp is necessary in AAS because
A. The width of an atom’s absorption band is narrow.
B. Cathode lamps are cheaper to operate and maintain.
C. Continuous spectrum lamps do not emit at the proper intensity.
D. Continuous spectrum lamps cause ionization of the molecules.

A

A. The width of an atom’s absorption band is narrow.

119
Q

Which species is used to bombard the sample in mass spectroscopy?
A. alpha
B. neutrons
C. electrons
D. protons

A

C. electrons

120
Q

A mass spectrum plots the intensity of each ion versus its
A. m/z ratio
B. absorbance
C. wavenumber
D. chemical shift

A

A. m/z ratio

121
Q

The peaks of the following bonds can be found at >3000 cm1 and in an IR spectrum EXCEPT
A. O-H bond
B. N-H bond
C. C-H bond
D. C-C bond

A

D. C-C bond

122
Q

A glass container that is half bottle (top) and half funnel (bottom) with a stopcock in the stem
of the funnel at the bottom used in separating immiscible liquids.
a. Separatory Funnel
b. Evaporating flask
c. Nessler’s Tube
d. Funnel

A

a. Separatory Funnel

123
Q

The selective dissolution of the analyte from a sample. The sample can be either a solid
material or a liquid, such as a water solution.
a. Fractional distillation
b, Extraction
c. Dilution
d. Fusion

A

b, Extraction

124
Q

Diethyl ether is highly flammable and also highly volatile that can result in an explosion due to
a flame source igniting the vapors in a lab in which it is being used. The following are the safety
precautions except:
a. avoiding open flames
b. working in a fume hood
c. storing the containers in explosion-proof refrigerators
d. use of plastic containers, which slow the peroxide formation

A

d. use of plastic containers, which slow the peroxide formation

125
Q

An extraction in which an analyte or its liquid solvent is extracted via contact with a solid
material (sorbent) as the solution passes through a cartridge containing the sorbent.
a. solid phase extraction
b. solid-liquid extraction
c. liquid-liquid extraction
d. none of the above

A

a. solid phase extraction

Solid Phase Extraction (SPE):

In this method, a liquid sample is passed through a solid material (sorbent) that selectively retains the analyte(s) of interest while allowing other components to pass through. This technique is commonly used for sample preparation in analytical chemistry.
Solid-Liquid Extraction:

This method involves extracting a substance from a solid matrix using a liquid solvent, typically done by soaking or percolating the solid with the solvent.
Liquid-Liquid Extraction:

This technique involves separating compounds based on their solubility in two different immiscible liquids, usually an organic solvent and water.

126
Q

Any reaction that emits noxious vapors should be performed in a _______.
a. laminar hood
b. chemical fumehood
c. biosafety cabinet
d. none of the above

A

b. chemical fumehood

127
Q

The following chemicals are less dense than water, and thus would be the top layer in an
extraction experiment except:

a. N-Hexane
b. Benzene
c. Toluene
d. Methanol

A

d. Methanol

In an extraction experiment, substances that are less dense than water will form the top layer when mixed with water. Therefore, N-hexane, benzene, and toluene will all float on water due to their lower densities.

Methanol, while also less dense than water, has a polar nature and can mix with water, thus it does not form a distinct top layer when added to water.

128
Q

The process by which an impure crystalline substance is purified by the dis- solving and
subsequent reconstitution of the crystals such that both soluble and insoluble impurities are
removed.
a. Crystallization
b. Recrystallization
c. Precipitation
d. None of the above

A

b. Recrystallization

Recrystallization is a technique used to purify solid compounds. The process involves dissolving the impure crystalline substance in a suitable solvent at an elevated temperature and then allowing the solution to cool slowly. As it cools, the pure compound crystallizes out, while the soluble impurities remain in the solution, and any insoluble impurities are removed through filtration.

Crystallization refers to the formation of solid crystals from a solution, but it doesn’t specifically imply the purification of an impure substance.

Precipitation is a process where a solid forms from a solution during a chemical reaction, but it is not specifically a method for purifying crystals.

Crystallization is about forming crystals from a solution, which may or may not be pure.

Recrystallization is specifically about purifying a substance by dissolving and then reforming the crystals to separate out impurities.

129
Q

In a purge-and-trap procedure, volatile analytes can be purged from a liquid sample by He
sparging, vigorous bubbling of He through the sample. The analytes are then desorbed by heating
the cartridge. analyzed by:
a. Gas Chromatography
b. HPLC
c. IR Spectrometry
d. HPTLC

A

a. Gas Chromatography

130
Q

If the analyte is too dilute for the chosen method, its concentration may be increased in any
number of ways.
a. Controlled evaporation of the solvent
b. Perform an extraction that results in a smaller solution volume for the same quantity of
analyte.
c. evaporate the analyte solution to dryness and then reconstitute (i.e., redissolve) with a
smaller volume of solvent.
d. All of the above

A

d. All of the above

131
Q

Ways of protecting sample from decomposition or deterioration:
a. storing the sample in a refrigerator
b. protecting it from light
c. protecting it from exposure to air or humidity
d. All of the above

A

d. All of the above

132
Q

Which of the following nonpolar organic solvents that are often used for extracting analytes
from aqueous solutions is more toxic and requires proper handling?
a. n-hexane
b. toluene
c. diethyl ether
d. chloroform

A

d. chloroform

n-Hexane: Generally considered less toxic, though it can cause neurological effects with prolonged exposure.

Toluene: Moderately toxic; can affect the nervous system but is often used with appropriate safety precautions.

Diethyl Ether: Highly flammable and can cause respiratory irritation; has some toxicity, but the primary concern is flammability.

Chloroform: More toxic compared to the others listed. It can cause significant health issues with prolonged exposure, including liver and kidney damage, and is a suspected carcinogen. Proper handling and ventilation are crucial when using chloroform.

133
Q

Chemically converting the analyte to a form that is stable so that the quantity of the analyte
can be determined indirectly by analyzing for the derivative.
a. Precipitation
b. Fusion
c. Derivatization
d. Volatilization

A

c. Derivatization

134
Q

This is a physical property of an organic compound often used to identify compounds or to check the
purity of the compound.
a. Melting point
b. Boiling point
c. Index of refraction
d. None of the above

A

Melting Point:

The melting point is a physical property that indicates the temperature at which a solid becomes a liquid. It is often used to identify pure compounds because pure substances have a sharp melting point. If impurities are present, the melting point typically decreases and broadens, making it a useful measure for assessing purity.

135
Q

Organic compounds are made of comparatively of ___________, which is the cause of their low
melting and boiling point.
a. Strong ionic bonds
b. Strong covalent bonds
c. Weak ionic bonds
d. Weak covalent bonds

A

d. Weak covalent bonds

Weak Covalent Bonds:

Organic compounds primarily consist of covalent bonds between carbon and other elements (like hydrogen, oxygen, nitrogen, etc.). In many organic compounds, these covalent bonds are not as strong as ionic bonds, and the intermolecular forces (such as van der Waals forces) between the molecules are relatively weak. This is a significant reason why many organic compounds have lower melting and boiling points compared to ionic compounds or compounds with strong intermolecular forces.

136
Q

The process used to separate insoluble solid component of a mixture from the soluble components in
a given solvent.
a. Sieving
b. Filtration
c. Decantation
d. Partitioning

A

b. Filtration

137
Q

A purification technique in which an impure solid is completely dissolved in a minimal amount of hot, boiling solvent, and the hot solution is allowed to slowly cool and the crystallized solid is then filtered away from the impurities.
a. Precipitation
b. Sublimation
c. Crystallization
d. Distillation

A

c. Crystallization

138
Q

Since the boiling point is dependent on the atmospheric pressure, the liquids will boil at a
temperature lesser than their boiling points if they were distilled in an atmosphere having lower
pressure. What purification technique is based on this principle?
a. Fractional Distillation
b. Vacuum Distillation
c. Steam Distillation
d. Sonication

A

b. Vacuum Distillation

This is a technique that uses ultrasonic waves to agitate a liquid, often used for mixing or breaking down particles, but it is not related to the principles of boiling point reduction through pressure changes.

139
Q

A type of distillation which involves the separation of miscible liquids. The basic principle is
that different liquids boil and evaporate at different temperatures. When the mixture is heated, the
substance with lower boiling point boil first and convert into vapors.
a. Fractional Distillation
b. Vacuum Distillation
c. Steam Distillation
d. None of the above

A

a. Fractional Distillation

140
Q

Defined as that temperature at which the vapor pressure of the liquid is equal to the
atmospheric pressure.
a. Melting Point
b. Boiling Point
c. Viscosity
d. Conductivity

A

b. Boiling Point

141
Q

A separation process for temperature sensitive substances and is used for separating miscible
liquid base depending upon their volatilities.
a. Fractional Distillation
b. Vacuum Distillation
c. Steam Distillation
d. Sonication

A

c. Steam Distillation

142
Q

Drying agents commonly used for drying solutions in organic solvents are
a. Calcium Chloride, Magnesium sulfate, Potassium carbonate
b. Potassium Hydroxide, Magnesium sulfate, Sodium sulfate
c. Calcium Chloride, Potassium Permanganate, Sodium sulfate
d. Magnesium sulfate, Sodium sulfate, Sodium Hydroxide

A

a. Calcium Chloride, Magnesium sulfate, Potassium carbonate

Calcium Chloride (CaCl₂): A highly effective drying agent that can absorb water from organic solutions.

Magnesium Sulfate (MgSO₄): Commonly used due to its effectiveness and rapid action in absorbing moisture.

Potassium Carbonate (K₂CO₃): Also used as a drying agent, especially in cases where other drying agents may not be suitable.

143
Q

For the most common drying agents such as sodium sulfate or magnesium sulfate, the
crystals form larger clumps when they absorb water. After standing for a short period the crystals
are removed by _____________-, and the solution is then relatively free of water.
a. filtration or decantation
b. oven drying
c. room temperature drying
d. heating on a hotplate

A

a. filtration or decantation

144
Q

_______________ when used as a drying agent combines with acids and phenols. It should not be
used to dry solutions containing acids unless it is desired to remove them also.
a. Potassium carbonate
b. Sodium sulfate
c. Magnesium sulfate
d. None of the above

A

a. Potassium carbonate

145
Q

In order to use a drying agent, it is just added to the solution using a ______ then the solution is
stirred or swirled or shaken and set aside to settle for a couple of minutes.
a. stirring rod
b. rubber policeman
c. spatula
d. forceps

A

c. spatula

Stirring Rod: While it is used to stir solutions, it is not typically used for adding solid substances like drying agents.

Rubber Policeman: This is a tool used to help scrape out residues from glassware but is not typically used for adding drying agents.

Forceps: These are used for grasping or holding objects but are not practical for adding drying agents to a solution.

146
Q

Drying agents should be
a. insoluble in the solvent to be dried as well
b. unreactive toward both the solvent and the solute
c. remove water quickly and can be easily removed by filtration
d. All of the above

A

d. All of the above

147
Q

A vacuum filtration setup replaces the Erlenmeyer flask with a vacuum flask with a side arm and the
glass funnel with a porcelain filter funnel known as a ____________.
a. Separatory funnel
b. Buchner funnel
c. Simple stemmed funnel
d. Ground glass funnel

A

b. Buchner funnel

148
Q

This glassware is used mainly for liquid-liquid phase extractions, which is a technique that allows
for the separation of products by using solvents with different polarities or hydrophobicities.
a. Separatory funnel
b. Buchner funnel
c. Simple stemmed funnel
d. Ground glass funnel

A

a. Separatory funnel

149
Q

Heating mantles are designed to safely heat a ______________ flask with varying volumes.
a. Erlenmeyer flask
b. Florence flask
c. Volumetric flask
d. Round-bottom flask

A

d. Round-bottom flask

150
Q

Heating equipment used when the temperature of the reaction does not need to exceed 100 °C.
a. Water bath
b. Hotplate
c. Heating mantle
d. Bunsen burner

A

a. Water bath

151
Q

If the required temperature in heating needs to exceed 100 °C but not 250 °C, a ________________
can be used. If the temperature must exceed 250 °C, a __________ can be used.
a. silicon mantle, sand bath
b. water bath, sand bath
c. water bath, silicon mantle
d. hotplate, silicon mantle

A

a. silicon mantle, sand bath

152
Q

A heating apparatus allows for facile heating of a solution, but without the loss of solvent that would
result from heating in an open vessel.
a. distilling apparatus
b. reflux apparatus
c. rotary evaporator
d. kjeldahl apparatus

A

b. reflux apparatus

153
Q

Always use __________ to transfer solid reagents from the supply to the weighing boat. Never reuse
for different reagents as this can contaminate the stock reagents.
a. stirring rod
b. rubber policeman
c. spatula
d. forceps

A

c. spatula

154
Q

Liquids heated in laboratory glassware tend to boil by forming large bubbles of superheated vapor, a
process called ________.
a. bumping
b. boiling
c. bubbling
d. none of the above

A

a. bumping

155
Q

Cooling baths are frequently needed in the organic laboratory to control
a. exothermic reactions
b. to cool reaction mixtures before the next step in a procedure
c. to promote recovery of the maximum amount of crystalline solid from a
recrystallization
d. all of the above

A

d. all of the above

156
Q

Temperatures from 0° to 10°C can be achieved by mixing solid _________ into an ice/water
mixture.
a. sodium hydroxide
b. potassium sulfate
c. sodium chloride
d. sodium sulfate

A

c. sodium chloride

157
Q

A reflux setup uses a ________ flask containing a solvent clamped to a stand, and a condenser is
fitted onto the flask.
a. erlenmeyer flask
b. florence flask
c. round-bottom flask
d. kjeldahl flask

A

c. round-bottom flask

158
Q

The basic process of _________ involves dissolving the substance in a solvent to remove
insoluble impurities then letting the desired compound crystallize.
a. distillation
b. sublimation
c. extraction
d. recrystallization

A

d. recrystallization

159
Q

The best liquid for use in a dry-ice bath is
a. ethyl ether
b. isopropyl alcohol
c. acetone
d. all of the above

A

c. acetone

160
Q

When heating a reaction,
a. flames should be avoided
b. the equipment should be assembled in such a way that heat can be removed rapidly
c. always be careful not to exceed the smoking temperature of the oil if an oil bath is used
d. all of the above

A

d. all of the above

161
Q

Organic components in solid samples are extracted from the matrix by continuously
washing the solid with a volatile solvent in a specialized piece of glassware
a. Soxhlet extraction
b. Ultrasonic extraction
c. Filtration
d. Rotary evaporation

A

a. Soxhlet extraction

Soxhlet Extraction: This is a specialized technique used to extract organic compounds from solid samples. The apparatus allows for continuous washing of the solid with a volatile solvent, which evaporates, condenses, and then re-dissolves the target compounds from the solid matrix. This process maximizes the extraction efficiency.

Ultrasonic Extraction: This method uses ultrasonic waves to agitate the solvent and improve the extraction efficiency but does not involve continuous washing like Soxhlet extraction.

Filtration: This is a separation technique that physically removes solids from liquids but does not involve the extraction of organic components.

Rotary Evaporation: This is used to remove solvents from solutions by evaporation but does not involve the extraction of organic components from solid samples. A rotary evaporator (sometimes abbreviated to rotavap) is a piece of equipment primarily used to remove solvent from a sample through “evaporation under reduced pressure”.

162
Q

Glass cuvettes are typically for use in the wavelength range of visible light, whereas fused
quartz tends to be used for ____________ applications.
a. microwave
b. IR
c. uv/visible
d. none of the above

A

c. uv/visible

163
Q

The technique used to identify a functional group in an organic molecule is
a. coulometry
b. X-rayfluorescence
c. Infrared spectrometry
d. Conductimetry

A

c. Infrared spectrometry

164
Q

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.

A

c. the stationary phase is non polar and the mobile phase is relatively polar.

165
Q

In professional chemistry, IR has largely gone out of fashion, replaced by more informative methods
specifically:
a. NMR. b. Gas Chromatography c. Thin Layer Chromatography d. ICP/MS

A

a. NMR

166
Q

An instrument that uses a light source to pass through a sample chamber and detects metal ions and
organic compounds.
a. IR b. HPLC c. LC/MS d. UV-visible spectrophotometer

A

d. UV-visible spectrophotometer

167
Q

A rhythmic movement along the line between the atoms so that the interatomic distance is either
increasing or decreasing.
a. Vibration b. Stretch c. Rotation d. degree of polymerization

A

b. Stretch

168
Q

Bend, results in a change in bond angle. The motions are called:
a.scissoring b. vibration c. stretch d. rotation

A

a. scissoring

169
Q

Most significant use of IR spectrophotometer
a. structural analysis b. molecular weight c. atomic structure d. separation of compounds

A

a. structural analysis

170
Q

Types of Quantum transition
a. nuclear b. bonding electron c. vibration/rotation of molecule d. a, b and c

A

d. a, b and c

171
Q

If the spectrum has a characteristic peak in the range of 2,500 to 2,000, the peak corresponds to
absorption caused by:
a. triple bonds b. double bonds c. aromatic HC d. alcohols

A

a. triple bonds

172
Q

In an IR spectrum, a peak in the 3600-3100/cm range typically signals the presence of:
a.C-H bond b. OH bond c. C=O bond d. COOH

A

b. OH bond

173
Q

How should the concentration of a colorless sample be determined?
a. Using a UV spectrophotometer c. Either a UV or VIS spectrophotometer
b. Using a VIS spectrophotometer d. Using an indicator solution and pH paper

A

a. Using a UV spectrophotometer

174
Q

The wavenumber of a transition is 2000 cm–1. In what part of the electromagnetic spectrum does this come?
a. Infrared c. Microwave.
b. Radiowave d. Ultraviolet-visible.

A

a. Infrared

175
Q

What is the name of an instrument used to measure the absorbance of a coloured compound in
solution?
a. Colourmeter c. Colorimeter
b. Calorimeter d. Coulometer.

A

c. Colorimeter

176
Q

The units of an IR spectrometer on the X-axis is
a. meter c .per centimeter
b. centimeter d. millimeter

A

c .per centimeter

177
Q

The unit of an NMR spectrum on the X-axis is
a. Hertz c. cm-1
b .ppm d. nanometer

A

b .ppm

178
Q

After taking an IR spectrum of a sample synthesized in the lab, you have 3 IR peaks. Peak A has
a 70 transmittance, peak B has a 50 transmittance, and peak C has a 5 transmittance. Which peak has the
greatest absorbance?
a. All the peaks have the same transmittance
b. Peaks A and B
c. Peak A
d. Peak C
e. Peak B

A

d. Peak C

179
Q

Which of the following are application of IR spectroscopy ?
a. To study polymer
b. To determined impurity
c. Identify functional group
d. All of the above

A

d. All of the above

180
Q

Which is range of absorption of functional group of C-N stretching?
a. 1000 – 1400 cm
b. 2000- 2400 cm.
c. 1700-1800 cm.
d. 1300 – 1400 cm

A

a. 1000 – 1400 cm

181
Q

Approximately where would a carbonyl peak be found on an IR spectrum?
a. 2800cm-1
b. The peak location will vary depending on the compound being analyzed.
c. 1700cm-1
d. 1000cm-1

A

c. 1700cm-1

182
Q

An unknown compound is analyzed using infrared spectroscopy. A strong, sharp peak is observed at a frequency of 1750cm-1. What functional group is present?

a. Alcohol b. Ester c. Saturated ketone d. Nitrile e. Unsaturated ketone

A

b. Ester

183
Q

An alcohol group in a compound would result in a broad dip around what part of the infrared (IR)
spectrum?
a. 3400cm-1. b. 2800cm-1. c. 1200cm-1. d. 1700cm-1

A

a. 3400cm-1.

184
Q

Which of the following statements is true concerning infrared (IR) spectroscopy?
a. Dipole moments between atoms
b. The movement of electrons to higher energy levels
c. The overall molecular weight of the molecule
d. The number of protons in a nucleus

A

a. Dipole moments between atoms

185
Q

What is the absorbance of an IR peak with a 25% transmittance?
a. 1.04
b. 2.50
c. 0.60
d. 0.81

A

c. 0.60

186
Q

Back diffusion occurs mostly in
a. SEC
b. Gas chromatography
c. HPLC
d. HPTLC
e. TIC

A

b. Gas chromatography

Back Diffusion: This refers to the movement of analyte molecules from a region of high concentration back into a region of lower concentration, often occurring when there is insufficient flow or mixing. In Gas Chromatography (GC), since gases have higher diffusion coefficients compared to liquids, back diffusion is more significant. This phenomenon can affect the separation efficiency by broadening peaks and reducing resolution.

Other Options:

SEC (Size Exclusion Chromatography): Back diffusion is less of an issue since the separation is based on size exclusion, and the mobile phase is liquid.

HPLC (High-Performance Liquid Chromatography): In liquid chromatography, diffusion is slower, so back diffusion is not as prominent.

HPTLC (High-Performance Thin Layer Chromatography): This is a planar technique, and diffusion plays a smaller role.

TIC (Total Ion Chromatogram): This is related to mass spectrometry, and diffusion doesn’t play a major role here.

187
Q

Which of the following techniques is least useful for structural determination of small organics?
a. UV spectroscopy
b. NMR
c. GC-MS
d. FT-IR

A

a. UV spectroscopy

188
Q

If several compounds are present in a sample which is developed on a TLC plate, a column of spots
is seen on the developed plate, with:
a. More polar compounds toward the top of the plate and less polar toward the bottom
b. More polar compounds toward the bottom of the plate and less polar toward the top
c. Lower boiling compounds toward the bottom of the plate and higher boiling toward the top
d. None of the above

A

b. More polar compounds toward the bottom of the plate and less polar toward the top

189
Q

Back flush is a technique used to
a. Clean an LC column from materials that deposited on the head of the column
b. Measure resistance to flow through a chromatographic system
c. Describe analyte envelope as it moves through the stationary phase
d. Peak shape
d. None of the above

A

a. Clean an LC column from materials that deposited on the head of the column

190
Q

Choose the correct result of channeling
a) ↓ in column efficiency
b) ↑ tailing
c) ↓ tailing
d) ↑ in column efficiency
a. a and b b. b and d c. a and c d. c and d

A

a. a and b

Channeling: This occurs when the mobile phase flows unevenly through a chromatography column, often due to poor packing or voids in the stationary phase. As a result:

It leads to a decrease in column efficiency because the analytes don’t interact uniformly with the stationary phase.
Increased tailing occurs because some analytes may pass through the column faster, causing broader and asymmetric peaks.
Other Options:

↑ in column efficiency is incorrect because channeling reduces separation performance.
↓ tailing is incorrect because channeling causes more tailing, not less.

191
Q

Which of the following is correct statement?

a. Resolution is proportional to the square root of the number of theoretical plates in a column
b. Resolution is inverse proportional to the square root of the number of theoretical plates
in a column
c. Resolution is proportional to the square of the number of theoretical plates in a column
d. Resolution is proportional to the number of theoretical plates in a column Resolution is
inverse proportional to the number of theoretical plates in a column

A

a. Resolution is proportional to the square root of the number of theoretical plates in a column

192
Q

Analyte that are extremely Hydrophobic (or) incompatible with water, a mobile phase that
contains no water is used. The separation is termed as
a. Reversed phase chromatography b. Normal phase chromatography
c. Non- aqueous Reversed phase chromatography
d. Aqueous Normal phase chromatography

A

c. Non- aqueous Reversed phase chromatography

Non-aqueous Reversed Phase Chromatography (NARP): This technique is used when the analyte is highly hydrophobic or incompatible with water. In NARP, the mobile phase contains no water, and instead, organic solvents are used to separate compounds that do not dissolve well in water.

Other Options:

Reversed Phase Chromatography typically involves a polar mobile phase (like water mixed with organic solvents) and a nonpolar stationary phase.
Normal Phase Chromatography uses a polar stationary phase and a nonpolar mobile phase but generally involves the use of water or a hydrophilic solvent.
Aqueous Normal Phase Chromatography involves an aqueous mobile phase, which would not be suitable for extremely hydrophobic analytes.

193
Q

Response time, is the time required for the detector to attain a percent of the final response signal
(98%). Too slow a response time leads to
a. Peak broadening
b. Peak tailing
c. Peak distortion
d. Peak doubling

A

c. Peak distortion

Response Time: This refers to the time a detector takes to reach a certain percentage (usually 98%) of its final signal after the analyte passes through. If the detector’s response time is too slow, it cannot accurately capture the shape of fast-moving peaks.

Peak Distortion: A slow response time will result in peak distortion, where the peak shape is not accurately represented due to delayed detection, making it appear stretched or misshaped.

Other Options:

Peak broadening occurs when the analyte spends too long in the column but is not directly related to detector response time.
Peak tailing is caused by poor interaction between the analyte and the stationary phase, not the detector’s response time.
Peak doubling is typically due to the presence of two compounds eluting closely, not due to slow detector response.

194
Q

TLC is generally used as a qualitative analytical technique for
a. Determining the number of components in a mixture
b. Checking the purity of a compound
c. Following the course of a reaction
d. All of the above

A

d. All of the above

195
Q

The process of release of Volatile/ soluble components of a GC or HPLC stationary phase
a. Bleed
b. Creep
c. Back flush
d. Back diffusion

A

a. Bleed

Bleed: In GC (Gas Chromatography) or HPLC (High-Performance Liquid Chromatography), bleed refers to the release of volatile or soluble components from the stationary phase into the mobile phase. This can lead to baseline noise, contamination, or interference in the chromatographic analysis, affecting sensitivity and accuracy.

Other Options:

Creep: Refers to the gradual movement or deformation of materials under stress, not specific to chromatography.
Back flush: A technique used in chromatography to reverse the flow of the mobile phase to clean the column or elute strongly retained compounds.
Back diffusion: Refers to the diffusion of analytes back into the mobile phase after elution, more common in gas chromatography.

196
Q

Retention factor, k’, describe
a. The distribution of an analyte between the stationary and the mobile phase
b. The migration rate of an analyte through a column
c. The velocity of the mobile phase A and b
d. b and c

A

b. The migration rate of an analyte through a column

197
Q

For Over-Pressured Layer Chromatography (OPLC), the in correct statement is
a. A TLC technique in which sorbent layer is firmly pressed against a cover
membrane and solvent is forced through sorbent layer
b. It is a type of planar chromatography
c. It has advantage over HPLC that viscous solvents can be used
d. The development of chromatogram is slower than that of TLC

A

d. The development of chromatogram is slower than that of TLC

198
Q

Channeling, denotes the presence of an empty volume (void) within a packed column leads to.
a. Band narrowing
b. Peak splitting
c. Increase in column efficiency
d. Decreased Tailing

A

b. Peak splitting

199
Q

Which of the following is not an advantage of HPLC over GC?
a. More versatile in adjusting separation parameters
b. A greater number of theoretical plates
c. Applicable to wider range of analytes
d. None of the above

A

c. Applicable to wider range of analytes

200
Q

Absorption in chromatography is a process of
a. Partitioning
b. Attenuation
c. Bulk phenomenon
d. Surface property

A

a. Partitioning

201
Q

In GC, retention depends upon the

a. Vapor pressure and polarity of the solute
b. Size and charge of the solute
c. The method of sample introduction
d The type of detector used

A

a. Vapor pressure and polarity of the solute

202
Q

The mobile phase in Gas Chromatography
a. Polar solvents
b. Non-polar solvents
c. Carrier gas
d. None of the above

A

c. Carrier gas

203
Q
  1. It is a chromatography technique where the mobile phase moves over an adsorbent. The separation
    takes place through differential migration which occurs when the solvent moves along the powder spread
    on the glass plates.
    a. TLC
    b. HPLC
    c. GC
    d. SEC
A

a. TLC

204
Q

The principle of separation in Gas-Solid Chromatography is _______________.
a. Absorption
b. Size exclusion
c. Adsorption
d Ion exchange

A

c. Adsorption

205
Q

The mobile phase in TLC can either be a single liquid or mixture of liquids. Some commonly used
mobile phases are:
a. Benzene-methanol
b. hexane-ethyl acetate-acetic acid
c. ether- diethyl ether-acetic acid
d. All of the above

A

d. All of the above

206
Q

In Thin Layer Chromatography, the stationary phase is made of ________ and the mobile phase is
made of ___________.
a. Solid, liquid
b. Liquid, liquid
c. Liquid, gas
d. Solid, gas

A

a. Solid, liquid

207
Q

Which of the following types of Chromatography involves the separation of substances in a mixture
over a 0.2mm thick layer of an absorbent.
a. Gas liquid
b. Column
c. Thin layer
b. Paper

A

c. Thin layer

208
Q

Thin layer chromatography is
a. partition chromatography
b. electrical mobility of ionic species
c. adsorption chromatography
d. none of the above

A

c. adsorption chromatography

209
Q

In Gas Chromatography, the basis for separation of the components of the volatile materials is the
difference in
a. partition coefficients
b. conductivity
c. molecular weights
d. mass

A

a. partition coefficients

210
Q

Adsorption chromatography applications:
a. Separation of amino acids.
b. Isolation of antibiotics.
c. Identification of carbohydrates.
d. All of the above

A

d. All of the above

211
Q

It is a chromatography technique where the mobile phase moves over an adsorbent. The separation
takes place through differential migration which occurs when the solvent moves along the powder spread
on the glass plates.
a. TLC
b. HPLC
c. GC
d. SEC

A

a. TLC

212
Q

The principle of separation in Gas-Solid Chromatography is _______________.
a. Absorption
b. Size exclusion
c. Adsorption
d Ion exchange

A

c. Adsorption

213
Q

The mobile phase in TLC can either be a single liquid or mixture of liquids. Some commonly used
mobile phases are:
a. Benzene-methanol
b. hexane-ethyl acetate-acetic acid
c. ether- diethyl ether-acetic acid
d. All of the above

A

d. All of the above

214
Q

Gas chromatography can be performed in which of the following ways?
a. only in columns
b. only on plane surfaces
c. either in columns or plane surfaces
d. neither in columns or plane surfaces

A

c. either in columns or plane surfaces

215
Q

Thin Layer Chromatography Chamber is used to develop plates. It is responsible to
a. Keep a steady environment inside which will help in developing spots
b. Prevents the solvent evaporation
c. Keeps the entire process dust-free.
d. All of the above

A

d. All of the above

216
Q

Ready-made plates are used which are chemically inert and stable. The stationary phase on the plate
has a fine particle size and also has a uniform thickness.
a. Reverse phase column
b. TLC plates
c. Normal column
d. None of the above

A

b. TLC plates

217
Q

After pouring the mobile phase into the TLC chamber, a __________is placed in the mobile phase
to maintain equal humidity.
a. moistened filter paper
b. wet cotton
c. kimwipe
d. none of the above

A

a. moistened filter paper

218
Q

In TLC, once the spots are developed, the plates are taken out and dried. The sample spots can be
observed under a ____________ light chamber.
a. Florescent
b. UV
c. LED
d. None of the above

A

b. UV

219
Q

In TLC, the mobile phase moves by ___________action.
a. gas pressure
b. capillary
c. liquid pressure
d. vapor pressure

A

b. capillary

220
Q

The designation for the tube in which the stationary phase in instrumental chromatography is
contained.
a. column
b. capillary
c. connecting tubes
d. rubber tubing

A

a. column

221
Q

Analytical GC is the use of GC solely for quantitative or qualitative analysis. Preparative GC is the
use of GC to __________ a particular substance for use in another experiment or research.
a. isolate and purify
b. separate the components
c. quantify the components
d. identify and quantify

A

a. isolate and purify

Chemical Technician (5 decks)

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