Organic Chemistry 1 Lab Final Exam Practice Questions

organic lab policy requires that the instructor be notified of the following:
a) allergies to chemicals handled in the lab
b) pregnancy while taking the course
c) drugs of medication that may impair normal functioning
d) a and b only
e) all of the above

all of the above

true or false: organic solvents and other chemicals may enter the body through the skin

true

in the J.T. Baker SAF-T-DATA rating system, the hazard level of substance is rated on a scale of:
a) 0-4, with zero being minimum hazard, and 4 being maximum hazard.
b) 1-4, with 1 being minimum hazard, and 4 being maximum hazard.
c) 0-4, with zero being maximum hazard, and 4 being minimum hazard.
d) 1-10, with 1 being minimum hazard, and 10 being maximum hazard.

0-4, with zero being minimum hazard, and 4 being maximum hazard

true or false: physical properties such as solubility and melting point can be readily found in Material Safety Data Sheets for specific chemicals.

true

a lab instructor is authorized to deny a student entrance into the lab if the student is wearing:
a) a sleeveless garment
b) shorts
c) tank tops
d) open shoes
e) b and c only
f) all of the above

all of the above

according to Chemistry lab policy, students who are or become pregnant while taking this course must:
a) be cautious, but no other action is required.
b) work with a partner and let the partner handle all the chemicals.
c) drop the course immediately.
d) obtain a doctor's approval to stay in the course.

obtain a doctor's approval to stay in the course

true or false: students working in the organic lab are required to wear eye protection of the approved type. However, it's not necessary for students to wear safety glasses if they are not handling chemicals at the time.

false

the Hirsch funnel is a device used to perform:
A) a vacuum filtration to separate crystals from the solvent.
B) a chromatographic purification of the active ingredient.
C) a melting point determination of the final product.
D) a quicker evaporation of the solvent during the procedure.
E) none of the above.

a vacuum filtration to separate crystals from the solvent

according to melting point theory (technique 9 in the textbook), what effect do impurities typically have on the melting point of a substance?
a) impurities typically cause the melting point to decrease and the melting range to increase.
b) impurities typically cause the melting point to increase and the melting range to decrease.
c) impurities typically cause both the melting point and the melting range to increase.
d) impurities typically cause both the melting point and the melting range to decrease.

impurities typically cause the melting point to decrease and the melting range to increase

Assume that 215 mg of pure aspirin was obtained from a tablet. what is the percent recovery if the label on the bottle states that each tablet contains 350 mg of the active ingredient (aspirin)?
a) 0.61%
b) 61.43%
c) 6.14%
d) 1.63%

61.43%

True or false: crystallization is a technique that can be used to purify any substance in any physical state.

false

What factors affect the solubility of a substance in a given solvent?
a) its color
b) its polarity in relation to that of the solvent
c) temperature
d) a and b
e) b and c

b and c

the ideal solvent for crystallization:
a) dissolves the sample at high temperature, but not at low temperature.
b) dissolves the sample at all temperatures.
c) dissolves the impurities at high temperature, but not at low temperature.
d) dissolves the sample at low temperature, but not at high temperature.

dissolves the sample at high temperature, but not at low temperature

what factors come into consideration when selecting a solvent for crystallization?
a) the polarity of the substance to be purified
b) the polarity of the solvent under consideration
c) the solubility of the substance in the solvent under consideration at high and low temperatures
d) A and B
e) all of the above

all of the above

true or false: mixtures of solvents (such as water-ethanol) SHOULD NOT be used in crystallization experiments.

false

in crystallization experiments, the term "mother liquor" refers to:
a) the solution containing the solute at high temperatures.
b) the solvent selected for crystallization when pure.
c) the solution or supernatant that remains after crystals have formed at low temperatures.
d) the solvent that gives the highest yield of crystals of a particular substance.

the solution or supernatant that remains after crystals have formed at low temperatures

what are some common mistakes made when performing crystallizations?
a) heating the solid sample before adding the solvent
b) adding too much solvent to try to dissolve the solid at low temperatures
c) losing too much solvent through evaporation when heating at high temperatures
d) impatiently expecting that crystals will form instantly as soon as the solution starts to cool
e) all of the above

all of the above

true or false: the technique of liquid-liquid extraction can be used to purify solids or liquids.

true

If an impure sample is in solution in solvent 1, and one wishes to select an extracting solvent 2 for this sample, a requirement for solvent 2 is that
a) it must be miscible with solvent 1
b) it must be less polar than solvent 1
c) it must be of the same polarity as solvent 1
d) it must be immiscible with solvent 1
e) it must be more polar than solvent 1

it must be immiscible with solvent 1

true or false: in liquid-liquid extraction, the distribution coefficient K is defined as the concentration of sample obtained in the extracting solvent divided by the concentration of sample obtained in the original solvent.

true

which solvent is suitable for extracting solutes from aqueous solutions?
a) water
b) ethanol
c) methylene chloride (CH2Cl2)
d) all are suitable
e) none of the above

methylene chloride (CH2Cl2)

50 mg of an impure sample is dissolved in 1 mL of water. the sample is extracted once with 0.5 mL ether. if the distribution coefficient of this sample in the two solvents is 10, how much sample migrates to the ether after ONE extraction?
a) 12.5 mg
b) 8.33 mg
c) 47.62 mg
d) 41.7 mg

41.7 mg

25 mg of an impure substance is dissolved in 2 mL of solvent A. if a purification by extraction is desired using solvent B, which of the following statements applies?
a) it would be more efficient to extract once with a 1.0 mL portion of B than two times with 0.5 mL portions of B each time.
b) it would be more efficient to extract two times with 0.5 mL portions of B each time, rather than once with a 1.0 mL portion of B.
c) the same amount of substance would be extracted by performing one extraction with 1.0 mL of B, or two extractions with 0.5 mL portions of B each time.

it would be more efficient to extract two times with 0.5 mL portions of B each time, rather than once with a 1.0 mL portion of B

a sample is dissolved in water and this solution is shaken with methylene chloride to perform an extraction. after the layers separate, the aqueous layer will most likely be at the ____ and the organic (methylene chloride) layer will be at the ____.

water density = 1.00 g/mL
methylene chloride density = 1.33 g/mL

a) top / bottom
b) bottom / top
c) there is not enough information to answer the question

top / bottom

sometimes after performing an extraction the two layers will not separate, and an emulsion will form instead. what technique can be used to break this emulsion relatively quickly?
a) transfer the mixture to a centrifuge tube and spin it for a few minutes.
b) evaporate the two solvents and start all over, trying to be more careful.
c) simply allow the emulsion to stand for some time.

transfer the mixture to a centrifuge tube and spin it for a few minutes

when an extraction procedure calls for "drying the organic layer" that means:
a) heating the organic layer until all the water evaporates.
b) adding a drying agent such as anhydrous sodium sulfate, which traps water molecules and forms
crystals.
c) shaking the organic layer with distilled water and then discarding the water.
d) inserting a paper towel into the solution until it soaks up all the water.

adding a drying agent such as anhydrous sodium sulfate, which traps water molecules and forms crystals

in organic chemistry, the technique of chromatography is used to analyze and separate the components of a mixture. The separation of these components is primarily based on their differences in:
a) melting points
b) boiling points
c) distribution coefficient
d) polarity
e) solubility in water

polarity

in thin layer chromatography, the term "mobile phase" is used in reference to:
a) the TLC plate
b) the eluting solvent
c) the components of the sample under analysis
d) the solid support

the eluting solvent

in a TLC separation, it is expected that the more polar components of the mixture will:
a) move more slowly than the less polar components
b) dissolve more slowly than the less polar components
c) move at a rate independent of their polarity, since this parameter has no effect on a TLC separation
d) move faster than the less polar components
e) dissolve faster than the less polar components

move more slowly than the less polar

suppose the same substance is spotted on two different TLC plates and each plate is eluted using a different solvent. The more polar solvent will cause the sample to:
a) travel faster along the TLC plate
b) travel more slowly along the TLC plate
c) none of the above

travel faster along the TLC plate

in TLC, the Rf value is defined as:
a) the distance travel by the substance on the TLC plate
b) the distance travel by the solvent on the TLC plate
c) a divided by b
d) b divided by a
e) a x b

a divided by b

true or false: given the definition of Rf, it is expected that its value be inversely proportional to the polarity of the substance being separated.

true

true or false: when placing a TLC plate inside a developing chamber, it is necessary that the solvent level be below the
level of the sample, or the experiment will be ruined.

true

from the definition of Rf, its value should be greater for ____________, and lower for _____________.
a) faster moving substances; slower moving substances
b) slower moving substances; faster moving substances
c) none of the above

faster moving substances; slower moving substances

when the Rf values of the components of a mixture are all very close to 1, that means that:
a) the solvent is too polar for a good separation
b) the eluting solvent level was too low
c) the eluting solvent level was too high
d) the polarity of the solvent is too low for a good separation
e) the polarity of the solvent is optimal for a good separation

the solvent is too polar for a good separation

true or false: when loading a sample onto a chromatographic column, it is desirable that the sample solution be as concentrated as possible, rather than in dilute form.

true

which of the following is the highest polarity solvent, or solvent mixture?
a) 70% hexane - 30% acetone
b) hexane
c) methylene chloride
d) acetone
e) 80% acetone - 20% methanol

80% acetone - 20% methanol

all of the following practices should be avoided when running a chromatographic column, except for one. which is the correct practice to follow?
a) allowing the level of eluting solvent to fall below the level of the solid support.
b) using a high polarity eluting solvent to initiate the separation, then gradually switching to lower
polarity solvents.
c) making abrupt changes in solvent polarity in the middle of the separation.
d) using a low polarity eluting solvent to initiate the separation, then gradually switching to higher polarity solvents.

using a low polarity eluting solvent to initiate the separation, then gradually switching to higher polarity solvents.

true or false: it is possible that a single band that comes out of a chromatographic column can be shown to be a mixture when analyzed by TLC.

true

some chemical reactions require a reflux period. which of the following best describes the reflux process?
a) a process by which the reactants are mixed dry, then exposed to the action of hot steam to effect the reaction.
b) a process by which the reactants are mixed in a solvent, and then the solvent is heated until all of it evaporates.
c) a process by which the reactants are mixed in a solvent, and then the solvent is brought to a boil, allowing the solvent vapor to condense and fall into a container other than the reaction pot.
d) a process by which the reactants are mixed in a solvent, and then the solvent is heated until it reaches the boiling point.
e) a process by which the reactants are mixed in a solvent, and then the solvent is brought to a boil, allowing the solvent vapor to condense and fall back into the (same) reaction pot.

a process by which the reactants are mixed in a solvent, and then the solvent is brought to a boil, allowing the solvent vapor to condense and fall back into the (same) reaction pot.

boiling point is defined as:
a) the temperature at which bubbles first form in the solvent.
b) the temperature at which the heat capacity of the liquid equals that of its vapor.
c) the temperature at which the vapor pressure of the liquid equals 760 mm Hg.
d) the temperature at which the vapor pressure of the liquid equals the external pressure.
e) the temperature at which the vapor pressure of the liquid equals 1 atmosphere.

the temperature at which the vapor pressure of the liquid equals the external pressure.

true or false: the technique of simple distillation can be used effectively to separate mixtures of liquids whose boiling points are at least 100 degrees apart.

true

when using microscale equipment, a difference between a reflux setup and a simple distillation setup is the presence of a ____________ positioned between the reaction pot and the condenser.
a) reflux ring
b) Hickman head
c) spin vane
d) drying tube
e) thermometer

Hickman head

a common way to describe the oxidation of carbon in organic chemistry is as a gain of bonds to:
a) sodium
b) oxygen
c) hydrogen
d) potassium

oxygen

a common way to describe the reduction of carbon in organic chemistry is as a gain of bonds to:
a) sodium
b) oxygen
c) hydrogen
d) potassium

hydrogen

which of the following reactions are organic reductions?
a) conversion of an alcohol to a ketone
b) conversion of an aldehyde to an alcohol
c) conversion of a ketone to alcohol
d) a and b
e) b and c

b and c

which of the following reactions are organic oxidations?
a) conversion of an alcohol to a ketone
b) conversion of an aldehyde to an alcohol
c) conversion of an alcohol to an aldehyde
d)a and b
e) a and c

a and c

the prominent band in the center of the IR spectrum shown below (indicated by the arrow) is typical of molecules containing a(n) ______________ functional group.

1.70 cm-1

a) alcohol (OH)
b) carbonyl (C=O)
c) primary amine (NH2)
d) alkyne (C-C triple bond)
e) nitrile (C-N triple bond)

carbonyl (C=O)

the broad band to the left of the IR spectrum shown below (indicated by the arrow) is typical of molecules containing a(n) ______________ functional group.

3350 cm-1

a) alcohol (OH)
b) carbonyl (C=O)
c) primary amine (NH2)
d) alkyne (C-C triple bond)
e) nitrile (C-N triple bond)

alcohol (OH)

the IR spectrum of alkenes shows a sharp, small to medium intensity band near ______________ wave numbers, corresponding to the C=C double bond stretching vibration.


a) 3300
b) 1650
c) 1450
d) 3000
e) 1140

1650

taken together, the three bands indicated below by the arrows suggest that the molecule showing this IR
spectrum is likely to be a(n):

2820 cm-1 2720 cm-1 1710 cm-1

in the answer choices given below R represents an alkyl group.

a) alcohol (R-OH)
b) ketone (R2C=O)
c) primary amine (R-NH2)
d) aldehyde (RCH=O)
e) nitrile (R-CN)

aldehyde (RCH=O)

the textbook indicates that under the conditions of exp. 66, one of three possible products is obtained. if product (2) is obtained, which bands would be seen in the IR spectrum? frequency numbers are approximate.
a) 3350 cm-1
b) 2820 & 2720 cm-1
c) 1710 cm-1
d) a and b
e) a, b, and c

a, b, and c

the textbook indicates that under the conditions of exp. 66, one of three possible products is obtained. if product (3) is obtained, which band(s) would NOT be observed in the IR spectrum? frequency numbers are approximate.
a) 3350 cm-1
b) 2820 & 2720 cm-1
c) 1710 cm-1
d) a and c
e) b and c

2820 & 2720 cm-1

HBr, one of the reagents needed in part A of exp. 23, is generated in the pot by the reaction between:
a) NaBr and sulfuric acid
b) n-butyl alcohol and NaBr
c) n-butyl bromide and water
d) n-butyl alcohol and sulfuric acid
e) n-butyl bromide and sodium hydrogen sulfate

NaBr and sulfuric acid

true or false: according to the mechanism given in the textbook, a carbocation intermediate forms during the course of the reaction between n-butyl alcohol and HBr in part A of exp. 23.

false

according to the mechanism given in the textbook, what type of carbocation forms during the reaction between t-pentyl alcohol and concentrated HCl in part C of exp. 23?
a) a secondary carbocation
b) a primary carbocation
c) a tertiary carbocation
d) a resonance-stabilized carbocation
e) according to the textbook, no carbocation forms in this mechanism.

a tertiary carbocation

all the steps in the mechanism of the reaction between t-pentyl alcohol and HCl are reversible. this means that once t-pentyl chloride is formed, it may _____________ if allowed to stay in contact with water for too long.
a) evaporate
b) undergo further attack by chloride ion to produce a dichloride
c) become too wet and difficult to dry
d) slowly dissolve in the aqueous layer
e) revert back to the alcohol

revert back to the alcohol

in one of the experiments an alkyl halide was prepared from an alcohol by an Sn2 reaction. if the IR spectrum of the product shows a broad band centered around 3300 cm-1, that is an indication that:
a) the product contains ethers produced by side reactions.
b) the product contains alkenes produced by side reactions.
c) the product is contaminated with the starting material.
d) the product is contaminated with inorganic salts.
e) the reaction was complete and the product is pure.

the product is contaminated with the starting material