OChem Lab Final
When taking a melting point, at what rate should you raise the temperature when close to the melting point? a. 2-3 degrees a minute b. 200-300 degrees a minute c. 0.2-0.3 degrees a minute d. 20-30 degrees a minute
a. 2-3 degrees a minute
A student isolates 127.30 mg of crude product after a reaction. After purifying this mixture using column chromatography, the student weighs the final product and determines they now have 91.35 mg of pure product. Calculate the percent recovery. a. 71.8% b. 28.2% c. 1.39% d. 139.4% c. 39.4%
a. 71.8%
How should long hair and beards be dealt with before entering the lab? a. All long hair should be tied back and secured. b. All long hair and beards must be kept clean so it is not a fire risk. c. All long hair should be tucked behind your ears before going into the lab. d. Beards should be shaved off and long hair cut to shoulder length
a. All long hair should be tied back and secured.
How should the alumina be disposed of at the end of the experiment? a. In a solid waste container. b. In the non-halogenated waste container c. In the halogenated waste container d. In the garbage can
a. In a solid waste container.
In general, what result does increasing eluent polarity have on the distance the compounds travel? a. In general, a more polar solvent causes the spots to travel further up the TLC plate b. In general, a more polar solvent gives worse separation c. In general, a more polar solvent gives better separation d. In general, a more polar solvent causes the spots to travel less on the TLC plate
a. In general, a more polar solvent causes the spots to travel further up the TLC plate
What precautions are needed with long hair and beards? a. No long hair or beards are allowed in lab b. Keep long hair tied back and away from flames and chemicals c. You must use a hair and/or beard net. d. Must be shampooed and clean
a. No long hair or beards are allowed in lab
Why is a flask never distilled to dryness? a. The flask could crack or break b. The flask will melt c. The flask could explode because of residue d. The flask could become charred
a. The flask could crack or break c. The flask could explode because of residue d. The flask could become charred
How would the melting range of a pure organic material be changed if there was a tiny shard of broken glass inside the melting point capillary? a. The melting range would not be affected. b. The melting range would decrease and get narrower. c. The melting range would increase and get narrower. d. The melting range would decrease and get broader.
a. The melting range would not be affected.
TLC spotters can be sharp. What is the major safety concern? a. They can puncture the skin and cause stab injuries b. They are hot and can cause burns c. They can damage the TLC plates d. They don't hold liquids well and the liquids can cause chemical burns
a. They can puncture the skin and cause stab injuries
Knowing a melting point of a compound can tell you BOTH its identity and purity. a. True b. False
a. True
If the fire alarm goes off while you are heating a reaction on an electric hot plate. What should you do? a. Turn off the heater and leave the lab. b. Stay and look after the reaction while an instructor finds out if it's a drill. c. You can leave the experiment running, but you should leave the lab room and follow campus evacuation procedures.
a. Turn off the heater and leave the lab.
Which of the following would be the best choice for neutralizing acid spilled on the benchtop? a. Use Sodium Bicarbonate b. Pour water over the spill. c. Mop up the spill with paper towels d. Leave the spill for your instructor to clean
a. Use Sodium Bicarbonate
Which of the following are NOT appropriate clothing to wear in lab? More than one answer may be selected. a. bare-back dress b. contact lenses c. a skirt that reaches mid-calf d. sandals e. a shirt that doesn't completely cover your stomach. f. tennis shoes g. pants that leave your ankles exposed h. short-sleeved shirt i. long pants that cover your ankles. j. shorts
a. bare-back dress b. contact lenses c. a skirt that reaches mid-calf d. sandals e. a shirt that doesn't completely cover your stomach. g. pants that leave your ankles exposed j. shorts
When packing a capillary tube for use in melting point analysis, it is important to take care not to: a. break the capillary tube. b. shake it. c. tap it on the bench. d. melt the capillary tube.
a. break the capillary tube.
If when you want to use the balance you find someone has spilled a solid reagent on the pan, you should: a. carefully brush the top of the balance, disposing of any material correctly b. wipe if off with a sponge c. put a piece of weighing paper over the spilled reagent and tare the balance. Then weigh your material as normal. d. use an acetone bottle to wash it off
a. carefully brush the top of the balance, disposing of any material correctly
Why should boiling stones never be added to a solution that is already boiling? a. if the liquid has become superheated, it could instantly and violently boil over upon addition of the chips b. the addition of the chips would cause numerous side reactions c. the glass could crack and break upon addition of the chips d. The boiling chips will crack and break upon addition
a. if the liquid has become superheated, it could instantly and violently boil over upon addition of the chips
What can be done to improve separation by column chromatography? More than one answer may be correct. a. increase column diameter b. increase the particle size of the alumina c. increase column length d. increase the polarity of the solvent
a. increase column diameter c. increase column length
Safety in the laboratory is a. is a shared responsibility b. the responsibility of the professor only c. the responsibility of the students only
a. is a shared responsibility
When you use a balance to weigh a reagent, you should weigh the solid a. on a tarred piece of weighing paper b. on a tarred piece of filter paper c. directly on the balance
a. on a tarred piece of weighing paper
When doing a melting point determination, if you miss the melting point you should: a. remove the sample from the apparatus and allow both the sample and the apparatus to cool. Then start again with the same sample. b. let the apparatus cool slowly and watch for the solidification point instead. c. throw the sample away and start completely over.
a. remove the sample from the apparatus and allow both the sample and the apparatus to cool. Then start again with the same sample.
Correct eye protection includes wearing a. safety goggles b. contact lenses c. vision correcting glasses d. safety glasses
a. safety goggles
A compound is often recrystallized at the end of an experiment. What is the reason for doing this? a. to purify it b. to decrease the yield c. to dissolve it d. to increase the yeild
a. to purify it
Gloves worn in lab must be removed before leaving lab, why? (choose all correct answers) a. When seen wearing gloves outside of the lab, the general perception can be that chemicals that are potentially harmful have been handled. b. Chemicals can be transferred from gloves to doorknobs, computers and cell phones. c. It prevents any possible contamination of other areas such as restrooms, elevators, and offices. d. If hazardous materials have been handled, it is possible that the gloves could be contaminated without the knowledge of the person wearing them.
all the above
Organic solvents are potential hazards because: (more than one answer may be correct) a. most organic solvents are flammable b. most organic solvents absorb through the skin c. most solvents are very volatile d. solvents can enter the body by inhalation
all the above
There is a definite correlation between orderliness and level of safety in the laboratory. In addition, a disorderly laboratory can hinder or endanger emergency response personnel. Which of the following housekeeping rules must be followed? (choose all correct answers) a. maintain a clean work space b. properly label and store all chemicals c. store all backpacks and jackets in the cubbies. d. never obstruct access to doorways
all the above
Your responsibilities for lab safety include: More than one answer may be correct. a. Knowing how to make your experiment safe in the case of a fire alarm. b. Being aware of the hazards of the chemicals in your experiment. c. Behaving in a professional manner in the lab. d. Knowing the location of the safety equipment. e. Following the general lab rules. f. Being aware of the hazards of the equipment. g. Knowing how to correctly dispose of the chemicals involved in your experiment. h. Knowing how and when to use the safety equipment.
all the above
What effect does compound polarity have on the TLC results? a. A more polar compound travels a greater distance up the plate b. A less polar compound travels a greater distance up the TLC plate
b. A less polar compound travels a greater distance up the TLC plate
Which statements are true about the principles of TLC? More than one answer may be correct. a. The stationary phase will always be more polar than the mobile phase b. Better separation will be achieved if one component adheres to the stationary phase more than the other component of the mixture does c. the solvent moves by capillary action. d. if the concentration of the component becomes too high, the spot will become a smear or begin to tail
b. Better separation will be achieved if one component adheres to the stationary phase more than the other component of the mixture does c. the solvent moves by capillary action. d. if the concentration of the component becomes too high, the spot will become a smear or begin to tail
At the end of an experiment, a student has an unused portion of reagent. Where should he or she place it? (select all correct answers) a. Pour the extra chemical down the drain b. Give it to another student who needs it to complete their experiment. c. Pour the extra chemical in the trash can d. Dispose of it in a proper waste container. e. Return it to the original container
b. Give it to another student who needs it to complete their experiment. d. Dispose of it in a proper waste container.
What is a safety concerns when using a UV light to expose spots on a TLC plate? a. it can bleach your clothes b. It can damage your eyes, if looked at directly c. It can cause stains to your skin d. It should not be inhaled
b. It can damage your eyes, if looked at directly
What does MSDS stand for? a. Maternal Security Dada Sheets b. Material Safety Data Sheets c. Mineral Security Directive Sheets d. Measurable Secretive Document Sheets
b. Material Safety Data Sheets
Which of the following statements best describes eutectic composition? a. The composition of a mixture of two components in an exact 1:1 ratio. b. The composition of a mixture of two components that generates the lowest possible melting point. c. The composition of a mixture of two components that can never dissolve in one another. d. The composition of a mixture of two components that generates the highest possible melting point.
b. The composition of a mixture of two components that generates the lowest possible melting point.
How should your work space be left when you have finished? a. With dirty glassware returned to your drawer. b. With glassware cleaned and returned to your drawer. c. With any dirty glassware in a tidy pile by the sink. d. With glassware cleaned and left in a tidy pile by the sink.
b. With glassware cleaned and returned to your drawer.
Which of the following statements about the procedure for column chromatography are true? More than one answer may be correct. a. letting the column dry out allows for better separation b. cracks in the alumina can affect separation of the compounds c. a flat surface at the top of the column is important for the sample compound to be evenly distributed d. Check that the column has a tight fitting frit at the bottom. e. Clamp the column as close to vertically as possible. f. Apply as much pressure as possible to elute the compounds g. the solvent line must be kept above the alumina level h. Check for cracks in the glass column before adding any chemicals
b. cracks in the alumina can affect separation of the compounds c. a flat surface at the top of the column is important for the sample compound to be evenly distributed d. Check that the column has a tight fitting frit at the bottom. e. Clamp the column as close to vertically as possible. g. the solvent line must be kept above the alumina level h. Check for cracks in the glass column before adding any chemicals
which of the following describes how solvents should be heated during a recrystallization? a. heat in a stoppered flask to keep the vapor away from any open flames. b. heat so that the solvent boils gently c. never let a solvent boil d. heat using a Bunsen burner
b. heat so that the solvent boils gently
How should acetone, ethyl acetate, or methyl tert-butyl ether be disposed of? (These organic solvents that contain carbon, hydrogen and oxygen.) a. in the solid waste container b. in the non-halogenated organic waste container c. flush it down the sink with plenty of water d. in the halogenated organic waste container
b. in the non-halogenated organic waste container
Which of the following is NOT true about chromatography? a. it can remove impurities from products b. it is used to separate elements from compounds c. it may be used in the pharmaceutical industry d. it may be used to separate two compounds in a mixture
b. it is used to separate elements from compounds
What would immediately be used if your clothing caught fire or if a large hazardous chemical spill had occurred on your clothing? a. fire extinguisher b. safety shower c. laboratory sinks d. eye wash station
b. safety shower
The TLC needs to be marked with two pencil lines (one where the spots are placed and one where the solvent front reaches.) Why can't these lines be drawn in pen? a. the ink will react with the sample b. the ink is likely to dissolve in the solvent and add extra spots to the TLC plate c. ink lines will not be visible on alumina, but pencil lines will show up d. pencil lines can be erased from the TLC plate if a mistake is made, and ink cannot
b. the ink is likely to dissolve in the solvent and add extra spots to the TLC plate
What error is introduced if the thermometer bulb is too high in the distillation apparatus? a. the recorded boiling point will be higher than actual because the bulb is not exposed to the hot vapor. b. the recorded boiling point will be lower than actual because the bulb is not exposed to the hot vapor c. the recorded boiling point will be higher than actual because hotter vapors travel higher up the condenser d. The recorded boiling point will be lower than the actual because hotter vapors travel higher up the condenser
b. the recorded boiling point will be lower than actual because the bulb is not exposed to the hot vapor
A boiling stone is added to a recrystallization solvent. Why is this? a. to add impurities to create crystals b. to prevent the solvent from bumping c. to help the solvent boil more quickly d. so that the solvent can be stirred
b. to prevent the solvent from bumping
A chemist runs a thin-layer chromatography (TLC) plate and marks the solvent as having traveled 6.1 cm up the plate. After visualization, the distance of the spot of interest is measured as having traveled 1.9 cm. Calculate the correct Rf value of this spot. a. 4.2 b. 3.2 c. 0.31 d. 1.9
c. 0.31
What is the typical melting range for a pure organic compound? a. 5 °C - 10 °C b. 0 °C c. 0.5 °C - 1.5 °C d. 0 °C - 5 °C
c. 0.5 °C - 1.5 °C
Compound A, 5 moles, with vapor pressure 200 mmHg at 50 oC, was mixed with compound B, 4 moles, with vapor pressure 400 mmHg at 50 oC to form a homogeneous solution. Calculate the vapor pressure of mixture at 50 oC. a. 600 mmHg b. 2,600 mmHg c. 289 mmHg d. 260 mmHg
c. 289 mmHg
During a melting point determination, it is normal to first take a rapid rough measurement followed by a slower more accurate measurement. Why is it important to allow the Mel-Temp to cool 15 °C below the melting point before placing the second capillary tube in, and to set the temperature increase to 1-2 °C per minute? a. A rapid temperature decrease will give a melting point range that is too high. b. A rapid temperature increase will give a melting point range that is too low. c. A rapid temperature increase will give a melting point range that is too high. d. A rapid temperature decrease will give a melting point range that is too low.
c. A rapid temperature increase will give a melting point range that is too high.
What effect do soluble impurities have on the melting point range of a substance? a. A soluble impurity will not affect the melting point range. b. The soluble impurity will narrow the melting point range. c. A soluble impurity will increase the melting point range.
c. A soluble impurity will increase the melting point range.
A drugstore offers denatured ethanol in concentrations of 70%, 95%, and 99% by weight. The 70% and 95% solutions are relatively inexpensive, but the 99% solution is very costly. Why? a. Complete separation will require multiple simple distillations. b. Complete separation will require multiple fractional distillations. c. Complete separation by distillation is impossible because the solutions form a low boiling azeotrope. d. Complete separation by distillation is impossible because the solutions form a high boiling azeotrope.
c. Complete separation by distillation is impossible because the solutions form a low boiling azeotrope.
Which of the following statements are necessary for a successful TLC experiment. Identify all the true statements. More than one answer may be correct. a. Carefully monitor the temperature of the solvent in the chamber. to achieve the best separation. b. Choose a solvent that is more polar than the compounds being separated. c. Do not disturb the developing chamber after putting the TLC plate inside. Do not move it or carry it around the lab. d. Cover the developing chamber with a lid. e. Use only pencil to mark the TLC plates. f. Ensure that the solvent level in the chamber is lower that where you spot the samples on the plate
c. Do not disturb the developing chamber after putting the TLC plate inside. Do not move it or carry it around the lab. d. Cover the developing chamber with a lid. e. Use only pencil to mark the TLC plates. f. Ensure that the solvent level in the chamber is lower that where you spot the samples on the plate
How fast should you heat the sample when measuring its melting point? a. Heat slowly until you get close to the expected temperature (start value listed in the procedure), then increase the rate. b. As fast as possible for the entire run. c. Heat quickly until you get close to the expected temperature (start value in the procedure), then slow the rate down. d. As slowly as possible for the entire run
c. Heat quickly until you get close to the expected temperature (start value in the procedure), then slow the rate down.
Which of the following statements best describes the rules for use of cell phones in the laboratory? Choose one answer. a. It is okay to use the calculator app on my cell phone while in lab b. It is okay to make phone calls in lab. c. It is not okay for me to use my cell phone while in the lab. d. It is okay for me to send text message in lab.
c. It is not okay for me to use my cell phone while in the lab.
When performing a distillation, how can you tell when your liquid is beginning to distill over? More than one answer may be correct. a. The temperature starts to rise as measured by the thermometer b. The liquid starts to boil in the pot c. Liquid droplets start to condense on the thermometer bulb d. The temperature remains constant after initially rising.
c. Liquid droplets start to condense on the thermometer bulb d. The temperature remains constant after initially rising.
Under which circumstances is it appropriate to work in the laboratory alone? a. So long as you have told someone what you are doing. b. So long as you are not doing a dangerous reaction. c. None d. So long as someone will be arriving soon.
c. None
Which one of the following statements follow the rules for safety goggles in the lab? a. Your ordinary vision correcting glasses are sufficient to protect your eyes in the laboratory. b. If you are only writing in your notebook and not using any chemicals, you can remove your safety glasses. c. Safety goggles must be worn at all times in the laboratory d. You only need to wear your safety goggles when you are doing something dangerous.
c. Safety goggles must be worn at all times in the laboratory
Two samples are spotted onto a thin-layer chromatography (TLC) plate, and the plate is developed and visualized. The result is that Sample A separates into three visible spots. Based on the given information, what conclusion can be made? a. Sample A contains less than 3 compounds. b. Sample A contains exactly 3 compounds c. Sample A contains at least 3 compounds d. Sample A contains more than 3 compounds
c. Sample A contains at least 3 compounds
If you feel unwell during the lab. What should you do first? a. Carry on with what you were doing. b. Go home. c. Speak to the instructor. d. Go to the campus health services.
c. Speak to the instructor.
After running a column with the goal of separating ferrocene from acetylferrocene, the student found a percent recovery of greater than 100%. What could attribute to this? (Select all that are correct.) a. Alumina eluted from the column and is contaminating the sample compound b. Sand eluted from the column and is contaminating the sample c. The sample was not dried properly and still contains solvent d. Ferrocene and acetylferrocene were not completely separated from each other.
c. The sample was not dried properly and still contains solvent d. Ferrocene and acetylferrocene were not completely separated from each other.
what is the result of adding too little boiling solvent to an impure sample and then cooling? a. crystals that are pure form b. large crystals are produced c. crystals with impurities remaining within them are produced d. no crystals are produced
c. crystals with impurities remaining within them are produced
Which of the following describes the technique for recrystallizing a compound? a. dissolve the sample in a large volume of solvent and then evaporate the excess solvent on a hot plate b. dissolve the sample in a minimum amount of cold solvent and then heat it to boiling. c. dissolve the sample in a minimum amount of boiling solvent and then allow to cool. d. add the solid sample to boiling solvent in a beaker using a spatula
c. dissolve the sample in a minimum amount of boiling solvent and then allow to cool.
Select the distillation technique that is most effective at separating compounds with boiling points that are within 40 °C of one another. a. vacuum distillation b. simple distillation c. fractional distillation d. steam distillation
c. fractional distillation
You have a sample that you are sure is Jaspersium, which has a literature melting range of 145-146 oC. Suppose you run your sample and observe a melting range of 139-145 oC. Your sample: a. is pure b. was heated too slowly c. is impure d. was heated too fast
c. is impure
what is the result of boiling the impure product with too much solvent and then cooling it on ice? a. small crystals are produced b. crystals with impurities remaining within them are produced c. no crystals are produced d. large crystals are produced.
c. no crystals are produced
Which of the following purposes is TLC mainly used for? a. cooling b. catalyst c. separation d. staining
c. separation
When a TLC plate was run and developed it showed only baseline spots. What change could be made to get the spot(s) to move further up the plate? a. spot a new plate and run it in a higher boiling solvent b. spot a new plate and run it in the same solvent c. spot a new plate and run it in a more polar solvent d. spot a new plate and run it in a less solvent
c. spot a new plate and run it in a more polar solvent
Why should the solvent level in the TLC chamber (jar) be below the line where the compounds are spotted? a. it allows the solvent to fully saturate the chamber (jar) b. it provides a better surface area for the solvent to travel c. the solvent might dissolve the compounds d. it provides the right volume of solvent for TLC without having to measure it
c. the solvent might dissolve the compounds
A chemist runs a thin-layer chromatography (TLC) plate and, after development and visualization, calculates the Rf value of one spot as 1.0. Select the correct location of the spot on the TLC plate. a. the spot has traveled 1/10 the distance traveled by the solvent. b. the spot is midway between the starting point and the solvent front c. the spot is in the same location as the solvent front. d. the spot is at the very top of the TLC plate
c. the spot is in the same location as the solvent front.
The product of an organic reaction is analyzed by column chromatography using silica as the stationary phase and toluene as the mobile phase. After several minutes it is noticed that the colored band due to the product is not moving down the column. What step can be taken to make the colored band elute from the column? a. use a less polar solvent b. heat the column to warm the compounds c. use a more polar solvent d. tap on the column to dislodge the compounds
c. use a more polar solvent
Once pure crystals have formed which technique is employed to isolate the pure solid? a. leave the mixture in an evaporation dish on your lab bench b. use vacuum filtration -- the product is found in the filtrate c. use vacuum filtration -- the product is found in the Hirsh funnel d. use gravity filtration -- the product is found in the filter paper
c. use vacuum filtration -- the product is found in the Hirsh funnel
You have a sample that you are sure is Jaspersium, which has a literature melting range of 145-146 oC. Suppose you run your sample and observe a melting range of 145-151 oC. Your sample: a. is pure b. is impure c. was heated too fast d. was heated too slowly
c. was heated too fast
If concentrated hydrochloric acid is spilt onto your skin, you should: a. wash it off with plenty of water from the lab eye wash station or safety shower. b. wipe it off using paper towel. c. wash it off with plenty of water from the tap. d. neutralize it with base
c. wash it off with plenty of water from the tap.
The melting point of salicylic acid is 159 °C and the melting point of acetylsalicylic acid, aspirin, is 134 °C. Which of the following melting point ranges would be appropriate for an impure aspirin sample that is contaminated with salicylic acid? a. 135 °C - 159 °C b. 159 °C - 172 °C c. 134 °C - 136 °C d. 121 °C - 130 °C
d. 121 °C - 130 °C
What effect do soluble impurities have on the melting point of a substance? a. The soluble impurity and compound of interest will display two distinct melting points. b. A soluble impurity will not affect the melting point. c. An impurity will increase the melting point. d. A soluble impurity will decrease the melting point.
d. A soluble impurity will decrease the melting point.
Which type(s) of molecular interactions determine a molecules melting range? a. Dipole-Dipole interactions b. Van der Waals forces c. hydrogen bonding d. All of the Above
d. All of the Above
Jewelry, such as rings and bracelets, should not be worn to the lab. Why? a. They are easily damaged by the chemicals in the lab. b. They can break glassware. c. They risk being stolen. d. Chemicals can become trapped under the jewelry and held in contact with the skin.
d. Chemicals can become trapped under the jewelry and held in contact with the skin.
Describe the movement of the ferrocene and acetylferrocene in your column during lab. What happened to the compounds as you added hexane to the column? a. both ferrocene and acetylferrocene moved down the column, with little separation b. neither compound moved down the column c. Only the acetylferrocene moved down the column, separating it from ferrocene d. Only the ferrocene moved down the column, separating it from acetylferrocene
d. Only the ferrocene moved down the column, separating it from acetylferrocene
What sort of experiments can be performed in the lab? a. Any interesting experiments that you have heard about on the internet. b. Any experiments that use the chemicals available in your lab. c. Any experiments you find on the American Chemical Society web site. d. Only those you are scheduled to perform and for which you have permission.
d. Only those you are scheduled to perform and for which you have permission.
What is the effect of soluble impurities in the sample? a. The melting point will be increased. b. The melting point will be unaffected. c. There will be two melting points observed. d. The melting point will be depressed.
d. The melting point will be depressed.
How long should a TLC plate run? a. Until the solvent reaches the top of the TLC plate b. about 5 minutes c. Until the solvent reaches the mid-point of the TLC plate. d. Until the solvent reaches the top pencil line, about 2 cm from the top of the plate
d. Until the solvent reaches the top pencil line, about 2 cm from the top of the plate
The CAS registry number is a. a rating of flammability b. a rating of reactivity c. a rating of toxicity d. a unique identifying number for each chemical
d. a unique identifying number for each chemical
When filling a melting point tube, to what level should you fill the tube with your sample? a. Full to the top. b. Half full. c. about 5 cm d. about 5 mm
d. about 5 mm
Why is it not advisable to wear contact lenses in the lab? a. Lenses could inadvertently fall out of the eye b. Chemical vapor could react with the lenses c. Chemical vapor could become trapped between the lenses and the eye d. all of the above
d. all of the above
Describe the movement of the ferrocene and acetylferrocene in your column during lab. What Would have happened to the compounds IF you added methyl tert-butyl ether to the column FIRST? a. Only the ferrocene would move down the column, separating it from acetylferrocene b. neither compound would move down the column c. Only the acetylferrocene would move down the column, separating it from ferrocene d. both ferrocene and acetylferrocene would moved down the column, with little separation
d. both ferrocene and acetylferrocene would moved down the column, with little separation
What can you do to elute a compound that is not coming off the column? a. change to a less polar solvent d. change to a more polar solvent c. cool down the column d. heat up the column
d. change to a more polar solvent
What should you do if you notice a piece of glassware has a crack in it? a. throw it away in the garbage can b. ignore the crack and continue using the glass piece c. swap it with someone else's glassware d. dispose of it in the glass waste container
d. dispose of it in the glass waste container
How should you dispose of 10 mL of dilute acid solution? Choose one option. a. in the halogenated organic waste container b. in the solid waste container c. in the non-halogenated organic waste container d. flush it down the sink with plenty of water
d. flush it down the sink with plenty of water
In column chromatography, which compounds elute first? a. those with lowest boiling point b. those with highest molecular weight. c. more polar d. least polar e. the most reactive
d. least polar
In column chromatography hexanes and methyl tert-butyl ether are the a. stationary phase b. absorbent c. sample compound d. mobile phase
d. mobile phase
Which of the following best describes the physical appearance of a compound when the END of its melting point range is reached? Select the one correct answer. a. the compound begins to evaporate b. Gas from the compound begins to condense on the side of the tube. c. the compound begins to convert to a liquid. d. the compound converts completely to a liquid
d. the compound converts completely to a liquid
In TLC, a piece of filter paper is often placed inside the developing jar to give faster and better results. Why? a. the filter paper absorbs the compounds from the TLC plate. b. the filter paper slowly filters the developing solvent. c. The filter paper prevents the solvent from evaporating from the jar d. the filter paper saturates the atmosphere of the developing jar with solvent vapors
d. the filter paper saturates the atmosphere of the developing jar with solvent vapors
What is the reason for the frit at the bottom of the column? a. to separate the compound from the absorbent b. to filter the solvent before collection c. to show where the bottom of the absorbent column is d. to keep the absorbent inside the column
d. to keep the absorbent inside the column
When setting up a column, what is the reason for adding a layer of sand on top of the adsorbent in the column? a. to stop the solvent from dissolving the sample b. to filter the solvent c. the weight of the sand helps pack the adsorbent more tightly d. to protect the adsorbent from being disturbed as solvent is added e. the sand prevents air bubbles from forming in the adsorbent
d. to protect the adsorbent from being disturbed as solvent is added
If you accidentally spill chemicals on your hand, your immediate action should be to: a. do nothing b. wipe off the spillage with a paper towel. c. fill out a safety incident report sheet. d. wash the affected area with plenty of water and alert the instructor.
d. wash the affected area with plenty of water and alert the instructor.
How should any excess hexanes and tert-butyl ether be disposed of at the end of the experiment? a. In a solid waste container. b. poured down the sink c. In the garbage can d. In the halogenated waste container e. In the non-halogenated waste container
e. In the non-halogenated waste container
NFPA: red
flammability
NFPA: blue
health
stationary phase
it is the solid separation medium
NFPA: yellow
reactivity
NFPA: white
special
mobile phase
the liquid that enters the column and carries the sample through the separation medium
eluent
the liquid that exits the column
