Lecture

Question 1

The following will cause drift errors in an analytical balance EXCEPT

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

Answer 1

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

Question 2

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

Answer 2

desiccator

Question 3

It is the nominal volume of water (or mercury) contained, or delivered by an article of volumetric glassware, at its reference temperature.

Answer 3

capacity

Question 4

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

Answer 4

25 mL graduated cylinder

Question 5

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.

Answer 5

None of the above.

Question 6

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?

Answer 6

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.

Question 7

To determine the density of a liquid, which of the following should be used?

Answer 7

pycnometer

Question 8

Which is TRUE for a 19/22 stopper?

Answer 8

diameter = 19 mm, height = 22 mm

(D/L)

Question 9

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

Question 10

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

Answer 10

all of the above

Question 11

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

Answer 11

all of the above

Question 12

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 nonhomogeneous sample from the bulk.

Answer 12

All

Question 13

Method of passing the sample through a metal or plastic mesh of a uniform cross-sectional area to separate particles into uniform sizes.

Answer 13

Milling

Question 14

Which of the following can remove a fairly large amount of water from a sample that contains thermally labile material?

Answer 14

freeze dryer

Question 15

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?

Answer 15

Successive weighings give the same mass.

Question 16

Sample preparation technique used prior to instrumental analysis of metals.

Answer 16

acid digestion

Question 17

Which of the following should NOT be used during dry ashing?

Answer 17

Glass

Question 18

Which of the following statements is/are TRUE?
I. 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.

Answer 18

All

Question 19

In the decomposition and dissolution of solids during sample preparation, which of the following is expensive and often the last resort?

Answer 19

Fusion technique

Question 20

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. have a low boiling point so it can be easily removed at a later
purification step

Answer 20

react with the desired substance

Question 21

This is done during liquid-liquid extraction to release the pressure build-up inside the separatory funnel during shaking.

Answer 21

venting

Question 22

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

Answer 22

shaking the separatory funnel containing the mixture very vigorously

Question 23

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

Answer 23

aqueous

Question 24

This is used to remove trace amounts of water in organic solutions. This can be added to the pooled organic layers before removal of the organic solvent.

Answer 24

drying agent

Question 25

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?

Answer 25

Multiple extraction using three 50-mL portions of ether.

Question 26

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

Answer 26

I and II

Question 27

Which of the following funnels should be used to filter hot mother liquor during recrystallization?

Answer 27

short stem funnel

Question 28

In crystallization, crystal phases can be interconverted by varying

Answer 28

Temperature

Question 29

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.

Answer 29

Two different pure substances have similar melting points.

Question 30

Which of the following techniques can be used to heat a reaction to 200ºC?

Answer 30

Place the reaction vessel in a sand bath with stirring.

Question 31

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

Answer 31

all of the above

Question 32

Where should a thermometer be placed to determine the boiling point of the distillate?

Answer 32

Inside the distilling flask and it should be just below the side arm of the flask

Question 33

An organic compound decomposes at its boiling point. What is the most appropriate method for the recovery of the solid organic compound?

Answer 33

steam distillation

Question 34

It allows for many successive distillations to take place at once. It contains indentations or a packing material with lots of surface area.

Answer 34

fractionating column

Question 35

The boiling point of a liquid is the temperature at which the vapor pressure is

Answer 35

equal to external pressure

Question 36

When the solid and liquid phases are in equilibrium, the temperature of the system

Answer 36

remains constant

Question 37

A liquid mixture that has a constant boiling point and whose vapor has the same composition as the liquid.

Answer 37

azeotrope

Question 38

What is the main purpose of heating under reflux?

Answer 38

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

Question 39

A reaction mixture needs to be cooled to -77ºC after refluxing. What is the best method to be used?

Answer 39

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

Question 40

The elution power of a mobile phase is determined by A. its overall polarity B. the polarity of the stationary phase C. the nature of the sample components D. all of the above

Answer 40

all of the above

Question 41

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.

Answer 41

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

Question 42

The height equivalent of a theoretical plate (HETP) has all of the 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 the column length is equal to the number of theoretical plates in the column.

Answer 42

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

Question 43

All of the following are common carrier gases from gas chromatography EXCEPT

Answer 43

Oxygen

Question 44

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

Answer 44

Poor resolution can be obtained.

Question 45

An air sample is subjected to gas chromatography for the analysis of Freon-11 (CCl3F). The detector that is most suitable for this analysis is

Answer 45

FID

Question 46

An advantage of HPLC over GC for the separation and measurement of high molecular weight compounds is that

Answer 46

The preparation of volatile derivatives is not necessary in HPLC.

Question 47

Reversed-phase chromatography refers to which of the following?

Answer 47

A polar stationary phase and a nonpolar mobile phase

Question 48

Which of the following has the correct order of elution (first to last) from an HPLC column containing a reversed-phase packing?

Answer 48

acetamide, acetone, dichloroethane

Question 49

In anion-exchange chromatography,

Answer 49

The column has (+) resin where (–) species bind.

Question 50

Which of the following is the correct order in which light passes through a UV-Vis spectrophotometer

Answer 50

source, monochromator, sample, detector

Question 51

Which light source should be used in the wavelength range of 340 to 1000 nm?

Answer 51

Tungsten

Question 52

What is the purpose of a monochromator?

Answer 52

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

Question 53

Why must solutions with high concentrations be diluted prior to analysis via Beer's Law?

Answer 53

The relationship between absorbance and concentration is not linear at high concentration.

Question 54

A solution containing 4.48 ppm KMnO4 (158.04 g/mol) exhibits 85.9% transmittance in a 1.00-cm cell at 520 nm. Calculate the molar absorptivity of KMnO4 at this wavelength.

Question 55

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.

Answer 55

Flame

Question 56

A hollow cathode tube lamp is necessary in AAS because

Answer 56

The width of an atom's absorption band is narrow

Question 57

A mass spectrum plots the intensity of each ion versus its

Answer 57

m/z ratio

Question 58

A soft ionization method in mass spectrometry that is typically applied to biomolecules that involves a laser striking a solid matrix to ionize the analyte without fragmentation or decomposition.

Answer 58

MALDI

Question 60

The peaks of the following bonds can be found at ≥3000 cm-1 and in an IR spectrum EXCEPT

Answer 60

C-C bond