CHEM 225 Lab Exam 1
In this lab, you will be using a ______apparatus to measure melting point ranges.
Mel-Temp
What is the name of the instrument that will be used in the lab to measure refractive index?
Abbe refractometer
True or False: Halogenated waste from the bromination test can be disposed of down the sink.
False
By a linear extrapolation from the boiling points of methanol (64.7 ºC), ethanol (78.37 ºC), 1-propanol (97 ºC), 1-butanol (117.4 ºC), and 1-pentanol (137 ºC), predict the boiling point of 1-hexanol in degrees Celsius. Hint: The correct answer is slightly different from the measured, literature value of the boiling point.
153-155
How many safety showers are located in LSB-115?
2
While directly measuring a melting point in the lab, you should use a setting on the apparatus so that the temperature rises no more than ___ to ____degrees per minute. (Enter a numerical value for each of the blanks.)
2 to 3
Rank the following possible types of intermolecular forces in organic compounds from lowest strength (1) to highest (4). 1. Ionic 2. Hydrogen 3. Dipole-dipole 4. Van der Waals
4, 3, 2, 1
A mixture consisting of 50 mL of cyclohexene and 50 mL of toluene is boiling in a round bottom flask. The vapors above the boiling liquid are: A. enriched in cyclohexene. B. enriched in toluene. C. the same composition as the liquid. D. none of the above.
A
As the strength of interactions between molecules increases, what tends to happen to the boiling point? A. The BP increases B. The BP decreases C. The BP remains the same
A
What test would yield a positive result for 1-butene? A. Bromination Test B. Iodoform Test C. TLC Test D. Beilstein Test
A
What test would yield a positive result for 3-octene? A. Bromination Test B. Iodoform Test C. TLC Test D. Beilstein Test
A
What test would yield a positive result for cyclopentene? A. Bromination test B. TLC test C. Iodoform test D. Beilstein test
A
Which of the following are we NOT performing a chemical test to confirm? A. Alcohol B. Alkene C. Aromatic ring D. Methyl ketone E. Halogen
A
When working in the organic chemistry lab, which of the following are required personal protective equipment (PPE)? (Select all of the correct answers below for full credit) A. Safety goggles or splash-proof safety glasses B. A full-length, long-sleeved lab coat C. Disposable gloves D. A face mask
A, B, C
When measuring the volume or mass of an organic liquid, which of the following represents POOR laboratory practice? Select all that apply. A. Placing a disposable pipette directly into the stock bottle to obtain the liquid. B.Pouring the liquid to the approximate volume first, then adjusting with a disposable pipette. C.Inverting the disposable pipette to made sure no liquid drains out during the transfer. D. Using beakers or Erlenmeyer flasks for volume determination. E. Returning any excess to the stock bottle in order to prevent waste. F.Determining the mass of a container and then removing it from the balance before transferring a liquid into it.
A, C, D, E
Measuring the boiling point of a compound can be used to ________ (Select all that apply) A. confirm the compound's identity B. determine the compound's structure C. calculate the compound's density D. assess the compound's purity
A, D
Match the following functional groups to the test that would give a positive result. A. Iodoform test B. TLC test C. Bromination test D. Beilstein test 1. Alkene 2. Aromatic Ring 3. Methyl Ketone 4. Halogen
A: 3 B: 2 C: 1 D: 4
A student performs a recrystallization similar to how we did it in lab to purify salicylic acid from sodium chloride using warm water as the solvent. After heating the mixture until all of the material dissolves, the solution cools and a white precipitate forms. The student then performs a vaccum filtration to separate the white precipitate from the solution. Where can the student find the sodium chloride? A. Collected in the Büchner funnel B. Dissolved in the water filtrate (the "mother liquor") C. Evaporated D. Vacuumed away into the house vacuum system
B
Crushing a solid compound into a fine powder results in a _____ melting point range than melting one large crystal. A. less accurate B. more accurate C. lower D. higher
B
The impure benzoic acid sample we will use in lab contains which of the following components? A. benzoic acid B. sodium acetate C. activated charcoal D. sodium chloride
B
What piece of glassware will you use for the iodoform test? A. Beaker B. Test Tube C. Erlenmeyer flask D. Round bottom flask
B
Which of the following compounds has the highest boiling point? A. hexane B. 2-hexanol C. 2-methyl-2-pentanol D. 2-hexanone
B
Which size round bottom flask would be the best to use to perform a simple distillation on 25 mL of liquid? A. 25 mL B. 50 mL C. 100 mL D. 250 mL
B
What test(s) would give a positive result for benzylacetone? (Select all that apply) A. Bromination Test B. Iodoform Test C. TLC Test D. Beilstein Test
B, C
What test(s) would give a positive result for bromoacetone? (Select all that apply) A. Bromination Test B. Iodoform Test C. TLC Test D. Beilstein Test
B, D
Maleic acid and malonic acid have very similar names, and coincidentally, very similar melting point ranges. Maleic acid melts between 134-136 °C, and malonic acid melts between 135-137 °C. If a student inadvertently returned some malonic acid to the maleic acid jar, which of the following melting point ranges would you expect to find of the maleic acid mixture now? A. 134-136 °C B. 135-137 °C C. 130-135 °C D. 136-140 °C
C
The faster one performs a melting point determination, the _____ the melting point range will be. A. faster B. slower C. less accurate D. more accurate
C
What is the source of the strongest intermolecular attractions in a sample of 1-heptanol? A. Ionic bonding B. Dipole-dipole C. Hydrogen bonding D. van der Waals dispersion forces
C
What is the step we will use to physically separate and collect the recrystallized benzoic acid? A. Melting it B. Boiling it C. Vacuum filtration D. Distillation
C
When measuring the boiling point of a liquid using a simple distillation apparatus, where should the thermometer bulb be placed? A. Against the glass on the bottom of the round-bottom from which the hot liquid is being distilled. B. Directly into the hot liquid but not touching the bottom of the flask. C. Into the hot vapors above the liquid. D. Into the receiving flask where the condensate is being collected.
C
At which of the following temperatures would benzoic acid be MOST soluble in water? A. 0 °C B. 20 °C C. 50 °C D. 90 °C
D
The major safety hazard with the Beilstein test is what? A. the UV light source B. the fact that bromine is very corrosive C. using a halogenated solvent D. using the Bunsen burner with the highly flammable test compounds
D
What is the source of the strongest intermolecular attractions in a sample of heptane? A. Ionic bonding B. Dipole-dipole C. Hydrogen bonding D. van der Waals dispersion forces
D
What physical property of organic compounds does recrystallization exploit to achieve purification? A. melting point B. molecular weight C. density D. solubility
D
Where are the safety showers in LSB-115 located? A. By the sinks B. By the windows C. On the center benches D. By the doors
D
Which of the following compounds has the highest boiling point? A. 1-pentanol B. 2-pentanol C. 3-pentanol D. cyclopentanol
D
Which of the following compounds has the highest boiling point? A. methanol B. ethanol C. 1-propanol D. 1-butanol
D
Which size round bottom flask would be the best to use to perform a simple distillation on 90 mL of liquid? A. 25 mL B. 50 mL C. 100 mL D. 250 mL
D
True or False: As long as you are wearing closed-toe, closed-heel shoes, the tops of your feet can be exposed since they are unlikely to become contaminated.
False
True or False: Beakers and Erlenmeyer flasks are good pieces of equipment to use for measuring an accurate volume.
False
True or False: Given the same number of carbons, the general trend is that linear alcohols have lower boiling points than branched alcohols.
False
True or False: Given the same number of carbons, the general trend is that primary alcohols have lower boiling points than secondary alcohols.
False
True or False: If you mix compound A (melting point range: 43-44 °C) with compound B (melting point range: 44-45 °C), then you will observe the mixture to have a melting point range of 43-45 °C.
False
True or False: In order to achieve better separation of a multi-component mixture, one should use a high VARIAC setting in order to perform the distillation as quickly as possible.
False
True or False: In the lab, melting points are measured as single temperature values.
False
True or False: The chemical tests must be done in a specific order in order to work properly.
False
True or False: When obtaining the liquids for the density measurements, any excess that is accidentally taken should be returned to the stock bottle.
False
True or False: Benzoic acid is more soluble in 5% aqueous sodium hydroxide than it is in water.
True
True or False: Impurities should be more soluble in the solvent than the desired material.
True
True or False: Safety goggles or lab safety glasses should be worn in the lab whenever chemicals are out and being handled by anyone in the room.
True
True or False: The general trend is that increasing number of carbon atoms leads to an increase in the boiling point of a compound.
True
The boiling point of a liquid is defined as the temperature where the liquid's vapor pressure matches the _______pressure.
atmospheric
When performing liquid-liquid extractions, the bottom layer should be removed through the ______, and the top layer should be removed through the _______.
bottom, top
Impure samples have melting point ranges that are both __________and ___________compared to a pure sample.
depressed, broadened
If 25 mL of ethyl acetate is mixed with 25 mL of aqueous sodium hydroxide, two layers will form and the _________layer will be on the top.
ethyl acetate
The phenomenon of melting point depression is used in every-day life during the winter whenever roads are salted. Ice and salt are mixed together to lower the melting point of water, making roads less slippery until colder temperatures. The precise composition of salt and ice to yield the lowest melting point temperature is with 23 wt% salt. This value is called the ______point for a mixture. (Be sure to spell your answer correctly.)
eutectic
An extraction ________is a convenient way to display each of the steps of a reactive (or acid-base) extraction.
flow chart
When distilling a 50/50 mixture of hexane and toluene, which of the two components in the mixture will you distill off first?
hexane
Organic acids and bases in their ________form are soluble in organic solvents, but the corresponding _______are more water-soluble. Therefore, converting acids and bases to the corresponding ______provides a convenient tool to separate acidic, alkaline and neutral organic compounds.
neutral, salts, salt
The ratio of concentrations of a solute in each layer is defined by the _________, K.
partition coefficient
One should never heat a closed system due to the _______that would build up, potentially leading to an ________of the glassware.
pressure, explosion
Because the presence of impurities lowers the melting point, the melting point can be a good indicator of purity: the ______the material, the ______its melting point, and the _____the melting point range.
purer, higher, narrower
Melting points are always measured as a ______.
range
What piece of glassware is used to perform liquid-liquid extractions?
separatory funnel
Crystals grow from __________solutions.
supersaturated
The refractive index for a given compound depends on what?
temperature and wavelength
The boiling point of a liquid is defined as the temperature at which the _________ of the liquid equals atmospheric pressure.
vapor pressure
Distillation is the process of _________a liquid, ________the vapor, and _________the condensate in another container.
vaporizing, condensing, collecting
Density is defined as mass per unit _________.
volume
